Background: Besides short stature, gonadal dysgenesis leading to a lack of oestrogen is one of the main characteristics of Turner syndrome (TS). In most TS girls, puberty is induced with exogenous oestrogens. Objective: To describe the pubertal development and uterine dimensions achieved by low-dose 17β-oestradiol (17β-E2) orally started at an appropriate age. Additionally, to determine whether serum hormone levels aid evaluation of pubertal progression. Design In 56 TS girls, we prospectively studied pubertal stage, serum E2, LH, FSH, SHBG and oestrone (E1), starting oestrogen treat- ment with a low-dose 17β-E2 (5 μg/kg/day) during GH treatment at mean (SD) age 12·7 (0·7) years. Hormone levels were measured at start, 3 months after start and after increasing 17β-E2 dosage. Uterine dimensions were measured in 39 TS women at age 19·9 (2·2) years. Results Althoughbreastandpubichairdevelopmentweresimilar to that in normal Dutch girls up to Tanner stage B5 and P5, respec- tively, breast development was 2 years later. Before oestrogen therapy, E2 levels were comparable to those in prepubertal girls. With a 17β-E2 dose of 5 μg/kg/day, these levels increased significantly, becoming comparable to normal late pubertal or adult concentrations, whereas SHBG levels were unchanged. At the adult 17β-E2 dose, SHBG had increased significantly. Uterus shape was juvenile in four (10·2%), cylin- drical in four and mature-adult shaped in 31 (79·5%) of TS patients. Conclusions During GH treatment in TS girls, normal breast development up to B5 can be mimicked, with just a 2-year delay. In a clinical setting, serum hormone levels provide no additional infor- mation for evaluating pubertal progression. After age-appropriate pubertal induction, uterine dimensions in women aged nearly 20 years were subnormal. It remains unclear whether this was related to E2 dosage, timing or duration, or factors related to TS.