We reviewed 177 patients with skeletal metastases, seen between 1984 and 1989, to define the characteristics of metastatic bone disease from an occult primary carcinoma. In 52 (30%) patients, the primary carcinomas could not be identified when the bone metastases were first diagnosed. This group was predominantly male, with intractable pain the most common symptom. The primary tumors were identified on antemortem evaluation in 28 (54%) patients after extensive examination. Among these, the primary tumor was in the lung in 9 patients, followed by liver (8), kidney (5), prostate (3), thyroid gland (2), and rectum (1). The identifiable occult malignancies possessed three common features: all were osteophilic tumors, all had a high incidence in the specific geographic area, and all were not amenable to early detection. The mean survival of these patients was 11 months. Current treatment modalities failed to affect the course of these patients, except for those with primary carcinomas of the kidney and prostate. This observation attests to our limitations in both the diagnosis and treatment of this problem. Efforts should be directed primarily toward excluding those common and/or treatable tumors only.