Background.Between 1939 and the 1960s, the synthetic estrogen diethylstilbestrol (DES) was given to millions of pregnant women to prevent pregnancy complications and losses. The adverse effects of prenatal exposure on the genitourinary tract in men and the reproductive tract in women are well established, but the possible effects on psychosexual characteristics remain largely unknown.Methods.We evaluated DES exposure in relation to psychosexual outcomes in a cohort of 2,684 men and 5,686 women with documented exposure status.Results.In men, DES was unrelated to the likelihood of ever having been married, age at first intercourse, number of sexual partners, and having had a same-sex sexual partner in adulthood. DES-exposed women, compared with the unexposed, were slightly more likely to have ever married (odds ratio [OR] = 1.1; confidence interval [CI] = 1.0–1.4) and less likely to report having had a same-sex sexual partner (OR = 0.7; CI = 0.5–1.0). The DES-exposed women were less likely to have had first sexual intercourse before age 17 (OR = 0.7; CI = 0.6–0.9) or to have had more than one sexual partner (OR = 0.8; CI = 0.7–0.9). There was an excess of left-handedness in DES-exposed men (OR = 1.4; CI = 1.1–1.7) but not in DES-exposed women. DES exposure was unrelated to self-reported history of mental illness in women.Conclusions.Overall, our findings provide little support for the hypothesis that prenatal exposure to DES influences the psychosexual characteristics of adult men and women.