Introduction In trans women (male‐to‐female transsexual persons), cross‐sex hormone therapy is administered to induce feminization. Breast development is an important part of feminization for most trans women.

Aim The aim of this study is to assess the effect of cross‐sex hormone therapy on breast development in adult trans women. Additionally, we aimed to investigate the benefit or harm of administration of progestogens on breast development.

Methods A review of the literature in Embase, Medline, The Cochrane Library, PsycINFO databases, PubMed, and Web of Knowledge until January 2014.

Main Outcome Measures Effects of cross‐sex hormone therapy and progestogens on breast development in trans women.

Results Only few studies with low quality of evidence addressed these topics. The available evidence suggests that breast development is insufficient for the majority of trans women and that type and dosage of hormonal therapy seem not to have an important role on final breast size.