The dihydrotestosterone content of normal peripheral and benign hyperplastic prostates was measured in tissue obtained at open surgical procedures on 29 men of ages 36 to 82 yr. The dihydrotestosterone content in normal prostates (mean +/- SE, 5.1 +/- 0.4 ng/g tissue) and in benign hyperplastic prostates (5.0 +/- 0.4) was similar. In 11 patients in whom both normal and hyperplastic prostatic tissue was harvested simultaneously at the same operation, there was no significant difference in the content of dihydrotestosterone in the two types of tissue. These findings fail to confirm the widespread belief that dihydrotestosterone content is elevated in benign hyperplastic prostates. Our data differ from the reported literature in one major respect: the dihydrotestosterone content of normal peripheral prostate in this study is three to four times higher than previously reported. This difference between the present and earlier studies was resolved by experiments performed on cadavers, which were the source of normal prostatic tissue used by other investigators. Dihydrotestosterone content was measured in seven cadavers ranging in age from 19 to 82 yr of age. The results of this experiment indicate that the dihydrotestosterone content of prostatic tissue removed at autopsy is factitiously low (0.7-1.0 ng/g tissue). This finding was confirmed by in vitro incubations of fresh prostatic tissue at 37 degrees C that demonstrated reduction of dihydrotestosterone content to low levels within 2 h. When taken together, these results indicate that when prostatic tissue is harvested appropriately, the dihydrotestosterone content of normal peripheral and hyperplastic tissues is the same. This finding should influence future research into the etiology of benign prostatic hyperplasia.