A 28-year-old woman with lymphangioleiomyomatosis had severe changes in the chest radiograph and recurrent pneumothoraces. Pathological tissue from the lung was progesterone receptor positive. After treatment with medroxyprogesterone her condition improved, but did not become clinically stable until after bilateral oophorectomy. Even after oophorectomy her condition deteriorated, when the dose of medroxyprogesterone was decreased. For one year after oophorectomy she has had no episodes of pneumothorax or breathlessness. In order to depress oestrogen activity further the anti-oestrogen drug tamoxifen was added to her usual treatment with medroxyprogesterone. During 2 weeks of treatment with tamoxifen and medroxyprogesterone marked increase of the changes in the chest radiograph were seen and a pneumothorax occurred. After discontinuation of tamoxifen the condition improved and has since been stable on medroxyprogesterone treatment.