Twenty-eight cases of prostatic adenocarcinomas have been selected and the mean argyrophil nucleolar organizer region (AgNOR) count for each case was evaluated. Nine of these tumors were of high, 13 of median and 6 of low differentiation. It was found that as the tumors became less differentiated, the AgNOR count increased (p less than 0.001). Stage of the disease, serum prostate-specific antigen (PSA) value, and DNA ploidy of all these cases have been examined as well but no statistically significant correlation among these three parameters and the AgNOR count was found.