Uma exsul is a restricted, vulnerable, and rare Mexican lizard that occurs only in fine aeolian sand deposits of the central Chihuahuan Desert. The reproductive cycle of this oviparous lizard was determined using monthly samples of both sexes collected throughout 1992 in the dry Laguna de Mayran in southwestern Coahuila, México. Females reached sexual maturity at a smaller snout–vent length (SVL; 60 mm) than males (73 mm). Reproductive activity of both sexes was synchronous and similar to other oviparous lizards. Mating and courtship occurred from March to June. Males exhibit testicular recrudescence during late winter (February and March) and maximum testicular volume occurred during June. The period of maximal testicular volume was positively correlated with increasing ambient temperature. Testis volume began to decrease in July, reaching minimum volume from August to October. Similarly, females began vitellogenesis during March and contained oviductal eggs from April to July. Females on average laid one or two clutches per breeding season. Mean clutch size based on oviductal eggs was 3.0 ± 0.1 SE (range = 3–5). Clutch size was positively correlated with female SVL. Hatchlings occurred during summer and early fall, when most of the annual rainfall occurs. Uma exsul and Mexican Uma paraphygas mature early and are short lived, consistent with an r-selected life-history strategy. In contrast, the North American species Uma scoparia, Uma inornata, and Uma notata exhibit K-selected characteristics.