The objective of this study was to assess the diagnostic strategy in identifying occult primary carcinomas in metastatic bone disease. The records of 29 patients seen between 1983 and 1993 were reviewed retrospectively. The patients had been evaluated nonuniformly with a wide array of diagnostic procedures. The primary tumor was identified in 22 patients antemortem, and in 2 patients postmortem. In 5 patients a diagnosis of the primary tumor was never obtained. Eleven of the primary tumors were carcinomas of the lung, 3 were prostatic carcinomas, 2 were carcinomas of the breast and 2 were malignant lymphomas. In 4 patients respectively a carcinoma of the kidney, the pancreas, the ovary or the stomach was found. One patient had a carcinoid tumor of the small intestine, and one had a retroperitoneal rhabdomyosarcoma. The average survival time after clinical onset of skeletal metastases was 12 months. We propose a flow sheet to evaluate this category of patients including a medical history, thorough physical examination, routine laboratory tests, chest radiography, bone scintigram, ultrasonography or computed tomography of the abdomen and biopsy of the most accessible metastasis. These tests allowed premortem diagnosis of the primary tumor in 75% of the cases. Biopsy should be considered the last test to be performed.