The labelling index in chronic nonspecific prostatitis ranges from 0.7-2.1%. This value is markedly higher than in nodular hyperplasia (0.4%) as well as in differentiated adenocarcinomas (0.6%). Increased labelling index could only be determined in glands adjacent to inflammatory foci. In recognition of these findings we believe that a correct evaluation of the cell proliferation in chronic prostatitis is only possible if each single cell can be evaluated, whether it is altered by inflammation or not. Therefore, solid tissue biopsies appear to be more suitable in autroadiographical studies than cytological material alone.