Objectives. Tall stature, a major characteristic of Marfan's syndrome, may be of concern to the family, particularly if the patient is a girl. Experience with treatment options-sex steroid or somatostatin analogue-for height reduction in girls is limited. We have evaluated our experience of estrogen treatment in girls with Marfan's syndrome attending the pediatric endocrine clinic in Glasgow between 1989 and 2005. Design and methods. Retrospective case note analysis combined with ascertainment of final/near final height, comparing outcome in treated and untreated girls. Cardiovascular health was assessed by examining aortic root diameter and blood pressure. Results. The study cohort comprised four treated and five untreated girls, of whom three were sisters. Treatment was started in the four girls at chronological age 10.0 (2.1) years, mean (SD) height 155.0 (9.8) cm, and Tanner breast stage B1 in three and B2 in one. Ethinyl estradiol was administered in stepwise incremental regimens, starting at 10 mg/day and reaching 100 mg/day after 10 weeks in two girls and starting at 2 mg/day and reaching a maximum of 30-50 mg/day over a 2- to 3-year period in two girls. Mean +/- SD (range) final/near final height of the four treated girls was 174.3 (2.6) (170.6-176.6) cm compared with 183.0 (6.9) (171.5-190.3) cm in the five untreated girls. No deaths occurred in the treated group while one untreated girl died from presumed arrhythmia aged 18 years. Aortic root diameter increased with age, by mean (SD) 5.0 (2.1) and 5.8 (4.5) mm in treated and untreated groups, respectively, but with no between-group differences after treatment. Conclusions. The estrogen doses used in this study are lower than in previous reports. The results, although unsuitable for statistical analysis due to small numbers, are encouraging with no adverse events being recorded. Future research should be multicenter in design.