On 170 patients with histologically proven carcinoma of the prostate scintigraphic studies of the skeleton using gamma camera and follow-up examinations were performed and compared with x-ray as well as serum alkaline and acid phosphatase. Osseous metastases in 47% had no radiological evidence and were only scintigraphically detectable. Positive scans were registered in 48% of the patients with prostatic cancer, 20% of them were positive due to metastases and 28% were false positive caused by osteoarthrotic and arthritic changes, sporadically by post-traumatic lesions and in 3 cases by Paget's disease. At the time of the initial diagnosis of prostatic cancer 21% of 159 patients studied scintigraphically had radiological or scan evidence of osseous metastases. Analyses corresponding stages of tumor revealed an unequivocal dependance of the frequency of metastases upon the extent of the primary tumor. The successful treatment is characterized by the decreased uptake of radioactivity primarily accumulated in skeletal metastases.