Richard Dean Anderson - Colonel/Brigadier General Jonathan J. "Jack" O'Neill
Don S. Davis - Major General George S. Hammond (Seasons 1-7)
Christopher Judge - Teal'c
Corin Nemec - Jonas Quinn (Season 6)
Michael Shanks - Dr. Daniel Jackson (Seasons 1-5, 7,8)
Amanda Tapping - Captain/Major/ Lt. Colonel Samantha Carter

Step through the stargate with SG-1, a team of soldiers and scientists, as they travel instantaneously to other planets to explore, forge alliances, defuse crises, establish trade, investigate ancient mysteries, and defend Earth from such hostile forces as the Goa'uld and the Replicators.

For eight years, from their base at the U.S. Air Force's Stargate Command in the Rocky Mountains, Gen. Jack O'Neill (Richard Dean Anderson), Dr. Daniel Jackson (Michael Shanks), Lt. Col. Samantha Carter (Amanda Tapping), and alien warrior Teal'c (Christopher Judge) have braved everything that the universe has thrown at them, from interstellar war and evil twins to death and ascension.

But changes are coming to SG-1 as it begins its ninth year of fearless service to Earth. New faces are joining the team: Maj. Cameron Mitchell (Ben Browder) will try to fill the very big shoes of former SG-1 leader O'Neill (who is now in charge in Homeworld Security), while Gen. Hank Landry (Beau Bridges) must adapt to the unique challenges of running Stargate Command, a posting unlike any other the military has to offer.

Offworld, SG-1 might have new friends ? or new foes ? in Vala (Claudia Black), a former Goa'uld host turned freedom-fighter; and Gerak (Louis Gossett Jr.), a Jaffa leader who vies with Teal'c for political control of the new Jaffa nation.