We studied reproductive characteristics of two syntopic whiptail lizards, Aspidoscelis marmorata and A. tesselata, inhabiting the northern Chihuahuan Desert. Reproductive characteristics studied were snout–vent length at sexual maturity, size of clutch, and volume of eggs. In A. marmorata, males and females were similar in snout–vent length, but body mass was larger in males than in females. Female A. tesselata were larger in snout-vent length and heavier than female A. marmorata. Mean size of clutch was 3.3 for A. marmorata and 3.5 for A. tesselata. Females of A. marmorata had larger volume of eggs than females of A. tesselata. Data suggest that both A. marmorata and A. tesselata respond to environmental factors of the region in different ways.