In this autopsy study the predictive values of positive and negative tests of core biopsies of the prostate were investigated. Core biopsies, which were performed after evisceration, were compared with macroscopic and microscopic findings of the entire prostatic gland. Of 107 investigated patients, 100 contained prostatic tissue in the core biopsies. In 11 patients the core biopsies contained carcinoma. All these patients had carcinoma in the tissue sections from the prostate. In 89 patients the core biopsy did not contain carcinoma. 88 of these patients had no carcinoma in the tissue sections from the entire specimens. However, in 1 patient a highly differentiated acinar adenocarcinoma was found. From these results the predictive value of a positive test is 11/11 = 100%, and the predictive value of a negative test is 88/89 = 98.5%. Core biopsy is a suitable method in diagnosing prostatic diseases and gives a very high accuracy when the core biopsy contains prostatic tissue.