The Stargate SG-1 RPG was developed by AEG and uses the d20 System (Requires the use of the Dungeons and Dragons Player's Handbook - Third Edition).
From the publishers website:
From the explosive TV series comes the hottest new roleplaying game of the year! Enter the stargate and explore the farthest reaches of the galaxy as a member of the SGC. Explore alien planets, learn the secrets of ancient cultures, and engage in pitched battles with the evil Goa'uld. Everything you need for hours of adventure is right here!
The Stargate SG-1 Roleplaying Game is a 400-page full-color hardbound volume containing everything you need to launch into the excitement and adventure of the Sci-Fi Channel's hottest weekly series. Based on the wildly popular Spycraft d20 game engine, this release opens up an entirely new venue of play for modern-day and sci-fi gamers alike, supported by one of the richest world tapestries on the market today!
* The first in an all-new line of science fiction adventure gaming supplements from the makers of Spycraft, Legend of the Five Rings, and 7th Sea!
* Fully compatible with the award-winning d20 system, using AEG's innovative Spycraft mechanics.
* Extensive background material on the SG program, its tactics, purpose, and resources, including rules for creating any SG-team member you can imagine.
* Detailed descriptions of the stargate itself, as well as the Cheyenne Mountain base that contains it.
* Comprehensive descriptions of several alien worlds, with full mechanical support.
* A brand new world-building system for Spycraft, allowing the GM to design any world he can imagine.
* New player character alien species - the Asgard, the Tok'ra, the Jaffa, and more.
* Background and rules for the Goa'uld System Lords - the devoted enemies of the SGC and all of humanity - including GM tips for designing campaigns around them.
* A complete synopsis for the first six seasons of the TV show.
In addition to the SG-1 Core Rules Book, there are the following sourcebooks available:
(2003) Fantastic Frontiers
(2004) Friends and Foes
(2004) Living Gods
(2004) First Steps