The Asgard were an extremely advanced race, one of the members of the Ancient Alliance of four great races. They resembled Roswell Greys and were a species who had regularly monitored and studied human development, having visited Earth without detection by Earth's satellites or telescopes. They were a friend to all, protector of all, except the Goa'uld, with whom they had been at war and with whom they had enforced an uneasy peace. As a species, the Asgard were a dying race. They reproduced exclusively through a process of enhanced cellular mitosis (cloning), and for nearly a thousand years had been physically incapable of achieving cell division through meiosis (sexual reproduction), a fact which accounted for their similarity in appearance. Asgard DNA was programmed to grow a clone to maturity in just three months, but the clone body was essentially an empty shell. As each Asgard's body failed, his consciousness was transferred into a newer, younger cloned version of himself.

The name Tok'ra literally means "Against Ra." The Tok'ra are a small alliance of Goa'uld resistance whose stated goal was the destruction of the System Lords and a change in the ways of the Empire. The great Queen Egeria had been a Goa'uld, but she broke away from the Goa'uld empire over 2000 years ago and came to Earth to stop the Goa'uld from taking humans as slaves. She founded the Tok'ra movement through her offspring before she was captured by Ra, who imprisoned her in stasis on Pangar, although for thousands of years she was believed to be dead. Both the Goa'uld and the Tok'ra are symbiotes, parasitical beings who pass on knowledge through genetic memory, and both can exhibit the characteristic glowing eyes and deep voice. However, the Tok'ra do not believe in taking hosts against their will. The Tok'ra symbiote blends with a host by choice, resulting in a truly symbiotic relationship in which the symbiote and host share a body, knowledge, and feelings.

The Jaffa were bred to have an abdominal pouch, similar to that of a marsupial, in which they carry a larval Goa'uld, or symbiote, to maturity.Although the Jaffa are a race of warriors bred specifically to serve the Goa'uld and enslave humans throughout the galaxy, they eventually came to be viewed by the SGC as a race indoctrinated from childhood to believe that the Goa'uld are their gods, and whose dependence upon symbiotes allowed them no choice but to serve. However, as dissent spread within the Jaffa ranks, nurtured by leaders such as Bra'tac, the Jaffa began to rebel against their false gods. The belief that a Jaffa's true strength is derived from the symbiote he carries slowly fell into question, and the drug tretonin gradually came to be seen as a means of freedom from enslavement. The Goa'uld no longer trusted the Jaffa priests with their young as they once did, and the Jaffa Rebellion eventually led to the defeat of the System Lords and the development of a free Jaffa Nation.

The Nox, a peaceful and highly advanced race native to P3X-774, are one of the members of the Ancient Alliance of four great races. Humanoid, but more advanced than anything that evolved on Earth, they possess a level of technology far beyond that of Earth or the Goa'uld, including the ability to create the effect of invisibility, to build floating cities, and to activate the stargate by thought alone. The Nox are peaceful, and defend themselves through illusion and mastery of the mind. Through their Ritual of Life, they can revive the dead. SG-1 first encountered the Nox while searching for the fenri on P3X-774, and they were revived from death by a Nox family after they had been killed by Apophis. Following SG-1's departure, the Nox intended to bury their stargate, making return impossible, however SG-1 has since encountered the Nox as allies to the Tollans and the Asgard.