The GAR regiment was made up of 2,664 clone troopers and officers led by a Jedi Commander or a clone regimental commander. Four of these regiments formed a Legion. However, the Republic also operated regiments of 1000 troopers.
Later, during the Imperial era, the Stormtrooper Corps, the successors to the GAR, were also divided into regiments. The regiment was also a unit in the Imperial Army and CompForce's order of battle.
In the Imperial order of battle, a regiment usually contained four battalions, though they could be expanded to contain up to eight. Army regiments contained 2,500 troops, with approximately 1,000 support personnel. Stormtrooper regiments were similar, but had no support personnel. CompForce regiments were also similar to Army regiments, but without security personnel. Imperial Sovereign Protectors were organized into regiments of 400.