Results of a questionnaire study of 91 Jamaican patients with homozygous sickle cell (SS) disease and 59 Jamaican control subjects of similar socioeconomic status indicated a mean delay of 2.3 years in age at menarche and of 3.9 years in age at first pregnancy in Ss disease. The mean interval between first sexual exposure and pregnancy was similar in the two groups. The delay in age at first pregnancy in SS disease resulted partly from the delay in puberty, but it also resulted from a further delay in first sexual exposure, with a mean interval between menarche and first sexual exposure of 2.6 and 4.4 years in control subjects and patients, respectively. Physical and social factors that related to this delay were reflected in the higher prevalence of casual unions in patients; this finding implied lesser sexual exposure. Although the similar interval between first sexual exposure and pregnancy did not suggest a lesser fertility in patients with SS disease, the number of infants born to patients with SS disease was less at all ages compared with Jamaican standards. This finding might reflect lesser fertility subsequent to the first pregnancy.