We have reviewed 29 patients whose first sign of a tumour was a bone metastasis. Two primaries were identified, lung adenocarcinoma and uterine adenocarcinoma and in 2 cases a presumptive diagnosis of tumours of the breast and prostate was made. The mean survival time was 3 months. When bone metastases are found in the absence of a primary tumour, investigation must include a clinical history, physical examination, routine laboratory tests and chest radiographs. Mammography should be done in women, particularly when there are palpable axillary nodes. Abdominal CT scanning and bronchoscopy should only be undertaken when there is a clinical indication.