Patients with prostate cancer frequently have osseous metastases which are qualitatively assessed with bone scannings. We have studied the quantitative evaluation of skeletal diseases by measuring bone mineral density (BMD) in the lumbar vertebrae and radius. Forty-four patients with prostate cancer, nine with non-prostatic urogenital cancer and 90 controls were entered in this study. Among the patients with prostate cancer, the values of BMD in the lumbar vertebrae were significantly higher in patients with osseous metastasis than in those without metastasis, whereas the values of BMD in the radius were insignificantly different. Most of the patients with high levels of BMD in the lumbar vertebrae had osseous metastatic disease with no relationship between BMD in the lumbar vertebrae and the radius. The values of BMD in the lumbar vertebrae where hot spot scans were observed were related to X-ray findings. The alterations of BMD levels in the lumbar vertebrae were quantitatively evaluable as responses to androgen deprivation therapy. Measurement of BMD is useful for the accurate diagnosis of osteosclerotic lesions. BMD measurements of the lumbar vertebrae compared with those in the radius were variable in individuals.