The age structure of the extinct giant Cape Verde skink Macroscincus coctei was studied using skeletochronology applied to 11 preserved males, 15 females, and one juvenile, collected at the end of the 19th century. Counts of lines of arrested growth (LAGs) indicated that in this species — which lived on islets with extreme natural conditions (e.g., hard aridity, lack of rainfall) — the maximum life span was estimated as 16 years for males and 12 years for females; the single juvenile was 4 years old. Although the sexes had similar mean ages, mean body length of males was significantly higher than that of females (283 versus 255 mm). There was no clear relationship between body length and estimated age, although the largest males were also the oldest. The analysis of LAGs revealed a sexual difference in growth rates, males reaching greater size earlier than females.