Sega Ages 2500 Series Vol. 14: Alien Syndrome (SEGA AGES 2500シリーズ Vol.14 エイリアンシンドローム) is a shoot'em up developed by h.a.n.d. Inc. and published by Sega. It was only released in Japan as a stand-alone game, in North America, it was released as part of the Sega Classics Collection.

The game is a remake of the classic arcade game, replacing the 2D graphics with real-time 3D.

A number of spaceships and space stations have been infested with alien creatures. You play a soldier who is sent to each of the infested ships and stations to rescue survivors and set up a time bomb to destroy the place and kill of the aliens.

The game is played from a top-down view. You can play alone or in 2-player co-op. There are two soldiers to choose from, Ricky and Mary. The goal in each level is to rescue enough survivors to unlock the exit, than leaving the level before the time runs out. After leaving the level, you have to pass a boss fight. If you do not beat the boss in time, you have to play through the whole level again.
All weapons in the game have infinite ammo and rapid fire. You either fire in the direction your moving or hold down a different fire button to lock the direction you fire at. Weapons are place in the walls of each level to pick them up. There are also maps on some walls of each level. If you come near them, a map of the level is displayed for a short time, including positions of the exit and the remaining survivors. Survivors have fixed positions in the levels, as the aliens have fixed them in slime blobs.