The records of 429 patients seen at the Centre Alexis-Vautrin in 1979 and 1980 with bony metastases were retrospectively reviewed to assess their natural history and survival. Breast was the location of primary lesion in 140 patients (32.6%), lung in 95 patients (22.1%) and prostate in 33 patients (7.7%). The primary tumor was of unknown origin in 42 cases (10.9%). The median survival from time of diagnosis was 5 months. Two and 5-year survival rates were 17.5 and 5.1% respectively. According to the nature of the primary tumor, 2 and 5-year survival periods for bony metastases were 36.4 and 7.9% in breast cancer, 33.3 and 15.2% in prostatic cancer, 4.3 and 2.1% in metastases of unknown origin, 2.1 and 0% in pulmonary carcinoma. Multivariate analysis revealed four factors to be of prognostic significance for survival: the nature of the primary tumor, the absence of local relapse, the disease-free interval and the absence of metastases in other sites. Patients with hormone-sensitive lesions or slowly-growing tumors had a better prognosis.