Using a silver staining, technique, Nucleolar Organizer Region-associated proteins (NORs) were studied on paraffin sections of 25 resected prostatic adenocarcinomas classified with Gleason grading and 11 hyperplastic lesions. Then 7 inclusions was selected for each grade of Gleason system and 7 inclusions of normal prostatic tissue. The mean numbers of argyrophilic nucleolar organizer regions (AgNORs) increased significantly (P less than 0.01) from normal prostatic tissue to Gleason 5. The data indicate that AgNORs counts may help distinguish between each grade of Gleason system. It was concluded that the AgNOR technique provides a significant kinetic evaluation of prostatic adenocarcinoma and its prognostic study.