The reproductive cycle of the Great Basin Collared lizard, Crotaphytus bicinctores was studied by a histological examination of museum specimens. Mean clutch size (n = 13) was 3.46 ± 1.1 SD, range: 2-6. Histological evidence indicates that two clutches may be produced in the same year. The reproductive season includes spring and early summer. There was a significant positive correlation between female body size (SVL) and clutch size (P = 0.03). The smallest reproductively active male and female C. bicinctores measured 81 mm and 78 mm SVL, respectively.