Fifty woman patients with adenoma or fibroadenoma, cystic, simple or complex dysplasias were treated with tamoxifen in daily doses of 20 mg. (2 tbs.) for 10 or 20 days during one or two menstrual cycles (in most cases 2 successive treatments) and uninterrupted for 30 or 90 days in menopaused women. A response was recorded in the main and associated lesions as well as in several similar lesions in the same case, and therefore, the results are analysed according to the lesion surface reduction in percentage. The different responses recorded can explain why the classification into responders and non-responders is difficult to make sometimes. 64% of the cases responded to the treatment. The results are most relevant if lesions are summed up and considered by type of lesion. Subjective symptoms disappeared or improved in 97% for mastodynia and 100% for dysmenorrhoea with a general decrease in menstrual bleeding. Short-term treatment of two tamoxifen cycles can be a means to select the responsive cases. They may be a preliminary stage before further endocrine treatment or before further surgery. This medicating pattern can solve some cases otherwise fit for surgery only.