Background Treatment with oestrogen to reduce the adult height of tall girls has been available since the 1950s. We undertook a retrospective cohort study to assess thelongterm effects of this treatment on fertility. Methods Eligible participants were identified from the records of Australian paediatric endocrinologists who assessed tall girls from 1959 to 1993, and from self referrals. Individuals included girls who had received oestrogen treatment (diethylstil boestrol or ethinyl oestradiol) (treated group) and those who were assessed but not treated (untreated group). Information about reproductive history was sought by telephone interview. Findings 1432 eligible individuals were identified, of whom 1243 (87% ) could be traced. Of these, 780 (63% ) completed interviews: 651 were identified from endocrinologists records, 129 were self referred. Treated (n=371) and untreated (n=409) women were similar in socioeconomic and other characteristics. After adjustment for age, treated women were more likely to have Background: With oestrogen to reduce the adult height of tall girls has been available since the 1950s. We undertook a retrospective cohort study to assess the longterm effects of this treatment on fertility. Methods Eligible participants were identified from the records of Australian pediatric endocrinologists who assessed tall Girls from 1959 to 1993, and from self referrals. Individuals included girls who had received oestrogen treatment (diethylstil boestrol or ethinyl oestradiol) (treated group) and those who were but not treated (untreated group). Information about reproductive history was sought by Of these, 780 (63%) completed interviews: 651 were identified from endocrinologists’ records, 129 were self referred. Treated (n = 371 ) and untreated (n = 409) women were similar in socioeconomic and other characteristics. After adjustment for age, tre ated women were more likely to have