A pilot study of Formestane or 4-Hydroxyandrostenedione (Lentaron), a new endocrine agent, was conducted on 18 postmenopausal patients with locally advanced and metastatic breast cancer. 16 patients were evaluable for response and objective responses were seen in 4 patients (25%). Stabilisation of disease was seen in 5 patients (32%). Out of 17 patients evaluable for toxicity, 3 (18%) reported adverse effects including hot flushes, lethargy and myalgia. Adverse effects were mild, transient and no patient required discontinuation of drug. Our study confirms that Formestane is a well tolerated endocrine agent with low toxicity and reasonable efficacy in postmenopausal patients with locally advanced and metastatic breast cancer.