Duke Nukem 3D: Atomic Edition (v1.4) was released in November 1996 as an upgrade to the original version of Duke Nukem 3D (v1.3d). There was also an update patch known as the Plutonium PAK that upgraded v1.3d of the game to v1.4. The Atomic Edition includes a new fourth episode, The Birth, with 11 new levels, one new weapon, the Microwave Expander, a new final boss for the fourth episode, the Alien Queen, two new enemies, the Protector Drone and the Pig Cop Tank, new graphics, new music, new voice-overs, and new sound effects. Three non-campaign levels, _SE.MAP, _ST.MAP, and _ZOO.MAP, are also included to showcase the capabilities of the Build engine and to show the additional content in the Plutonium PAK/Atomic Edition version of Duke Nukem 3D.
The Atomic Edition includes several improvements to the scripting language, such as allowing new enemies and items to be created without having to overwrite the existing ones. Another new feature in the Atomic Edition are the computer-controlled bots that allow fake multiplayer games to be played ("fake" because there are no other human players). The bots are capable of putting up a decent fight, and can be useful for testing a user-made map to see how well it will play in multiplayer mode, as well as providing practice.
In December 1996, another patch, this one unnamed, was released to upgrade v1.4 of the game to v1.5. The game is still called the Atomic Edition after this. This patch fixed a few more bugs in the game. The Plutonium PAK was used to update the original Duke Nukem 3D to version 1.4. The standalone Atomic Edition, by default, uses version 1.5.