Infertility was examined among 343 diethylstilbestrol-exposed and 303 unexposed daughters whose mothers participated in an evaluation of diethylstilbestrol use during pregnancy 35 years ago. Of the married individuals who were not using contraception and who were actively trying to conceive, a greater proportion of diethylstilbestrol-exposed women than unexposed subjects experienced primary infertility (33% versus 14%, p less than 0.001). Among those with primary infertility, abnormal hysterosalpingograms were observed in 46% of the diethylstilbestrol-exposed group and in none of the unexposed group (p less than 0.02), while tubal abnormalities were found in 42% of the exposed and in none of the unexposed (p = 0.02). First pregnancies were achieved by 40 (58%) women exposed to diethylstilbestrol and 18 (64%) unexposed subjects. Twenty-four (60%) of the exposed women and 15 (83%) of the unexposed individuals who conceived had a live-born infant who survived. The estimated cumulative rate of first pregnancy was 16% for the exposed group and 36% for the unexposed group at 12 months after the diagnosis of primary infertility (p less than 0.05).