diff --git a/src/db.c b/src/db.c
index 668a1193a..0a6481c8f 100644
--- a/src/db.c
+++ b/src/db.c
@@ -1388,7 +1388,7 @@ void getKeysFreeResult(int *result) {
 /* Helper function to extract keys from following commands:
  * ZUNIONSTORE <destkey> <num-keys> <key> <key> ... <key> <options>
  * ZINTERSTORE <destkey> <num-keys> <key> <key> ... <key> <options> */
-int *zunionInterGetKeys(struct redisCommand *cmd, robj **argv, int argc, int *numkeys) {
+int *zunionInterStoreGetKeys(struct redisCommand *cmd, robj **argv, int argc, int *numkeys) {
     int i, num, *keys;
     UNUSED(cmd);
 
@@ -1416,6 +1416,31 @@ int *zunionInterGetKeys(struct redisCommand *cmd, robj **argv, int argc, int *nu
     return keys;
 }
 
+/* Helper function to extract keys from following commands:
+ * ZUNION <num-keys> <key> <key> ... <key> <options>
+ * ZINTER <num-keys> <key> <key> ... <key> <options> */
+int *zunionInterGetKeys(struct redisCommand *cmd, robj **argv, int argc, int *numkeys) {
+    int i, num, *keys;
+    UNUSED(cmd);
+
+    num = atoi(argv[1]->ptr);
+    /* Sanity check. Don't return any key if the command is going to
+     * reply with syntax error. */
+    if (num < 1 || num > (argc-2)) {
+        *numkeys = 0;
+        return NULL;
+    }
+
+    keys = getKeysTempBuffer;
+    if (num>MAX_KEYS_BUFFER)
+        keys = zmalloc(sizeof(int)*(num));
+
+    /* Add all key positions for argv[2...n] to keys[] */
+    for (i = 0; i < num; i++) keys[i] = 2+i;
+    *numkeys = num;
+    return keys;
+}
+
 /* Helper function to extract keys from the following commands:
  * EVAL <script> <num-keys> <key> <key> ... <key> [more stuff]
  * EVALSHA <script> <num-keys> <key> <key> ... <key> [more stuff] */
diff --git a/src/server.c b/src/server.c
index 8ae5c64d9..6179d2f29 100644
--- a/src/server.c
+++ b/src/server.c
@@ -428,10 +428,18 @@ struct redisCommand redisCommandTable[] = {
 
     {"zunionstore",zunionstoreCommand,-4,
      "write use-memory @sortedset",
-     0,zunionInterGetKeys,0,0,0,0,0,0},
+     0,zunionInterStoreGetKeys,0,0,0,0,0,0},
 
     {"zinterstore",zinterstoreCommand,-4,
      "write use-memory @sortedset",
+     0,zunionInterStoreGetKeys,0,0,0,0,0,0},
+
+    {"zunion",zunionCommand,-3,
+     "read-only @sortedset",
+     0,zunionInterGetKeys,0,0,0,0,0,0},
+
+    {"zinter",zinterCommand,-3,
+     "read-only @sortedset",
      0,zunionInterGetKeys,0,0,0,0,0,0},
 
     {"zrange",zrangeCommand,-4,
diff --git a/src/server.h b/src/server.h
index 80df48881..685f929f5 100644
--- a/src/server.h
+++ b/src/server.h
@@ -2175,6 +2175,7 @@ void freeObjAsync(robj *o);
 int *getKeysFromCommand(struct redisCommand *cmd, robj **argv, int argc, int *numkeys);
 void getKeysFreeResult(int *result);
 int *zunionInterGetKeys(struct redisCommand *cmd,robj **argv, int argc, int *numkeys);
+int *zunionInterStoreGetKeys(struct redisCommand *cmd,robj **argv, int argc, int *numkeys);
 int *evalGetKeys(struct redisCommand *cmd, robj **argv, int argc, int *numkeys);
 int *sortGetKeys(struct redisCommand *cmd, robj **argv, int argc, int *numkeys);
 int *migrateGetKeys(struct redisCommand *cmd, robj **argv, int argc, int *numkeys);
@@ -2391,6 +2392,8 @@ void hstrlenCommand(client *c);
 void zremrangebyrankCommand(client *c);
 void zunionstoreCommand(client *c);
 void zinterstoreCommand(client *c);
+void zunionCommand(client *c);
+void zinterCommand(client *c);
 void zscanCommand(client *c);
 void hkeysCommand(client *c);
 void hvalsCommand(client *c);
diff --git a/src/t_zset.c b/src/t_zset.c
index 2ef02ac8a..9fddf37d1 100644
--- a/src/t_zset.c
+++ b/src/t_zset.c
@@ -2196,7 +2196,15 @@ dictType setAccumulatorDictType = {
     NULL                       /* val destructor */
 };
 
-void zunionInterGenericCommand(client *c, robj *dstkey, int op) {
+/* The zunionInterGenericCommand() function is called in order to implement the
+ * following commands: ZUNION, ZINTER, ZUNIONSTORE, ZINTERSTORE.
+ *
+ * 'numkeysIndex' parameter position of key number. for ZUNION/ZINTER command, this
+ * value is 1, for ZUNIONSTORE/ZINTERSTORE command, this value is 2.
+ *
+ * 'op' SET_OP_INTER or SET_OP_UNION.
+ */
+void zunionInterGenericCommand(client *c, robj *dstkey, int numkeysIndex, int op) {
     int i, j;
     long setnum;
     int aggregate = REDIS_AGGR_SUM;
@@ -2207,9 +2215,10 @@ void zunionInterGenericCommand(client *c, robj *dstkey, int op) {
     robj *dstobj;
     zset *dstzset;
     zskiplistNode *znode;
+    int withscores = 0;
 
     /* expect setnum input keys to be given */
-    if ((getLongFromObjectOrReply(c, c->argv[2], &setnum, NULL) != C_OK))
+    if ((getLongFromObjectOrReply(c, c->argv[numkeysIndex], &setnum, NULL) != C_OK))
         return;
 
     if (setnum < 1) {
@@ -2219,14 +2228,14 @@ void zunionInterGenericCommand(client *c, robj *dstkey, int op) {
     }
 
     /* test if the expected number of keys would overflow */
-    if (setnum > c->argc-3) {
+    if (setnum > (c->argc-(numkeysIndex+1))) {
         addReply(c,shared.syntaxerr);
         return;
     }
 
     /* read keys to be used for input */
     src = zcalloc(sizeof(zsetopsrc) * setnum);
-    for (i = 0, j = 3; i < setnum; i++, j++) {
+    for (i = 0, j = numkeysIndex+1; i < setnum; i++, j++) {
         robj *obj = lookupKeyWrite(c->db,c->argv[j]);
         if (obj != NULL) {
             if (obj->type != OBJ_ZSET && obj->type != OBJ_SET) {
@@ -2279,6 +2288,11 @@ void zunionInterGenericCommand(client *c, robj *dstkey, int op) {
                     return;
                 }
                 j++; remaining--;
+            } else if (remaining >= 1 &&
+                       !strcasecmp(c->argv[j]->ptr,"withscores"))
+            {
+                j++; remaining--;
+                withscores = 1;
             } else {
                 zfree(src);
                 addReply(c,shared.syntaxerr);
@@ -2399,20 +2413,37 @@ void zunionInterGenericCommand(client *c, robj *dstkey, int op) {
         serverPanic("Unknown operator");
     }
 
-    if (dstzset->zsl->length) {
-        zsetConvertToZiplistIfNeeded(dstobj,maxelelen);
-        setKey(c,c->db,dstkey,dstobj);
-        addReplyLongLong(c,zsetLength(dstobj));
-        notifyKeyspaceEvent(NOTIFY_ZSET,
-            (op == SET_OP_UNION) ? "zunionstore" : "zinterstore",
-            dstkey,c->db->id);
-        server.dirty++;
-    } else {
-        addReply(c,shared.czero);
-        if (dbDelete(c->db,dstkey)) {
-            signalModifiedKey(c,c->db,dstkey);
-            notifyKeyspaceEvent(NOTIFY_GENERIC,"del",dstkey,c->db->id);
+    if (dstkey) {
+        if (dstzset->zsl->length) {
+            zsetConvertToZiplistIfNeeded(dstobj, maxelelen);
+            setKey(c, c->db, dstkey, dstobj);
+            addReplyLongLong(c, zsetLength(dstobj));
+            notifyKeyspaceEvent(NOTIFY_ZSET,
+                                (op == SET_OP_UNION) ? "zunionstore" : "zinterstore",
+                                dstkey, c->db->id);
             server.dirty++;
+        } else {
+            addReply(c, shared.czero);
+            if (dbDelete(c->db, dstkey)) {
+                signalModifiedKey(c, c->db, dstkey);
+                notifyKeyspaceEvent(NOTIFY_GENERIC, "del", dstkey, c->db->id);
+                server.dirty++;
+            }
+        }
+    } else {
+        unsigned long length = dstzset->zsl->length;
+        zskiplist *zsl = dstzset->zsl;
+        zskiplistNode *zn = zsl->header->level[0].forward;
+        if (withscores && c->resp == 2)
+            addReplyArrayLen(c, length*2);
+        else
+            addReplyArrayLen(c, length);
+
+        while (zn != NULL) {
+            if (withscores && c->resp > 2) addReplyArrayLen(c,2);
+            addReplyBulkCBuffer(c,zn->ele,sdslen(zn->ele));
+            if (withscores) addReplyDouble(c,zn->score);
+            zn = zn->level[0].forward;
         }
     }
     decrRefCount(dstobj);
@@ -2420,11 +2451,19 @@ void zunionInterGenericCommand(client *c, robj *dstkey, int op) {
 }
 
 void zunionstoreCommand(client *c) {
-    zunionInterGenericCommand(c,c->argv[1], SET_OP_UNION);
+    zunionInterGenericCommand(c, c->argv[1], 2, SET_OP_UNION);
 }
 
 void zinterstoreCommand(client *c) {
-    zunionInterGenericCommand(c,c->argv[1], SET_OP_INTER);
+    zunionInterGenericCommand(c, c->argv[1], 2, SET_OP_INTER);
+}
+
+void zunionCommand(client *c) {
+    zunionInterGenericCommand(c, NULL, 1, SET_OP_UNION);
+}
+
+void zinterCommand(client *c) {
+    zunionInterGenericCommand(c, NULL, 1, SET_OP_INTER);
 }
 
 void zrangeGenericCommand(client *c, int reverse) {
diff --git a/tests/unit/type/zset.tcl b/tests/unit/type/zset.tcl
index e997bc66d..2f9eb823f 100644
--- a/tests/unit/type/zset.tcl
+++ b/tests/unit/type/zset.tcl
@@ -612,6 +612,12 @@ start_server {tags {"zset"}} {
             assert_equal 0 [r exists dst_key]
         }
 
+        test "ZUNION/ZINTER against non-existing key - $encoding" {
+            r del zseta
+            assert_equal {} [r zunion 1 zseta]
+            assert_equal {} [r zinter 1 zseta]
+        }
+
         test "ZUNIONSTORE with empty set - $encoding" {
             r del zseta zsetb
             r zadd zseta 1 a
@@ -620,6 +626,14 @@ start_server {tags {"zset"}} {
             r zrange zsetc 0 -1 withscores
         } {a 1 b 2}
 
+        test "ZUNION/ZINTER with empty set - $encoding" {
+            r del zseta zsetb
+            r zadd zseta 1 a
+            r zadd zseta 2 b
+            assert_equal {a 1 b 2} [r zunion 2 zseta zsetb withscores]
+            assert_equal {} [r zinter 2 zseta zsetb withscores]
+        }
+
         test "ZUNIONSTORE basics - $encoding" {
             r del zseta zsetb zsetc
             r zadd zseta 1 a
@@ -633,11 +647,29 @@ start_server {tags {"zset"}} {
             assert_equal {a 1 b 3 d 3 c 5} [r zrange zsetc 0 -1 withscores]
         }
 
+        test "ZUNION/ZINTER with integer members - $encoding" {
+            r del zsetd zsetf
+            r zadd zsetd 1 1
+            r zadd zsetd 2 2
+            r zadd zsetd 3 3
+            r zadd zsetf 1 1
+            r zadd zsetf 3 3
+            r zadd zsetf 4 4
+
+            assert_equal {1 2 2 2 4 4 3 6} [r zunion 2 zsetd zsetf withscores]
+            assert_equal {1 2 3 6} [r zinter 2 zsetd zsetf withscores]
+        }
+
         test "ZUNIONSTORE with weights - $encoding" {
             assert_equal 4 [r zunionstore zsetc 2 zseta zsetb weights 2 3]
             assert_equal {a 2 b 7 d 9 c 12} [r zrange zsetc 0 -1 withscores]
         }
 
+        test "ZUNION with weights - $encoding" {
+            assert_equal {a 2 b 7 d 9 c 12} [r zunion 2 zseta zsetb weights 2 3 withscores]
+            assert_equal {b 7 c 12} [r zinter 2 zseta zsetb weights 2 3 withscores]
+        }
+
         test "ZUNIONSTORE with a regular set and weights - $encoding" {
             r del seta
             r sadd seta a
@@ -653,21 +685,39 @@ start_server {tags {"zset"}} {
             assert_equal {a 1 b 1 c 2 d 3} [r zrange zsetc 0 -1 withscores]
         }
 
+        test "ZUNION/ZINTER with AGGREGATE MIN - $encoding" {
+            assert_equal {a 1 b 1 c 2 d 3} [r zunion 2 zseta zsetb aggregate min withscores]
+            assert_equal {b 1 c 2} [r zinter 2 zseta zsetb aggregate min withscores]
+        }
+
         test "ZUNIONSTORE with AGGREGATE MAX - $encoding" {
             assert_equal 4 [r zunionstore zsetc 2 zseta zsetb aggregate max]
             assert_equal {a 1 b 2 c 3 d 3} [r zrange zsetc 0 -1 withscores]
         }
 
+        test "ZUNION/ZINTER with AGGREGATE MAX - $encoding" {
+            assert_equal {a 1 b 2 c 3 d 3} [r zunion 2 zseta zsetb aggregate max withscores]
+            assert_equal {b 2 c 3} [r zinter 2 zseta zsetb aggregate max withscores]
+        }
+
         test "ZINTERSTORE basics - $encoding" {
             assert_equal 2 [r zinterstore zsetc 2 zseta zsetb]
             assert_equal {b 3 c 5} [r zrange zsetc 0 -1 withscores]
         }
 
+        test "ZINTER basics - $encoding" {
+            assert_equal {b 3 c 5} [r zinter 2 zseta zsetb withscores]
+        }
+
         test "ZINTERSTORE with weights - $encoding" {
             assert_equal 2 [r zinterstore zsetc 2 zseta zsetb weights 2 3]
             assert_equal {b 7 c 12} [r zrange zsetc 0 -1 withscores]
         }
 
+        test "ZINTER with weights - $encoding" {
+            assert_equal {b 7 c 12} [r zinter 2 zseta zsetb weights 2 3 withscores]
+        }
+
         test "ZINTERSTORE with a regular set and weights - $encoding" {
             r del seta
             r sadd seta a