Correlation between findings on bone gammagraphy and PSA levels in 144 patients with untreated prostate cancer are analyzed. With prevalence of metastatic disease in 57.6% cases and considering the predictive cut value of metastasis to be 20 ng/ml, there were positive and negative predictive values of 64.9% and 73.9%, with a diagnostic confidence of 66.6%. We conclude that bone gammagraphy is essential for staging prostate cancer even in patients with PSA below 20 ng/ml.