From the fetal period up to puberty the immature epithelium of the prostate glands, the prostatic ducts, the ejaculatory ducts and the seminal vesicles as well as the urothelium of the prostatic urethra are extensively positive for different keratin antibodies (antibody against keratins from human stratum corneum, broadly reacting antibody "AE1 and AE" and antibodies against the keratins 7, 8, 18 and 19) immunohistochemically. The epithelium of the ejaculatory ducts and seminal vesicles in addition regularly exprimates vimentin which is found in the epithelium of the prostate glands focally. During puberty, the immature epithelium of the prostate glands differentiates into the two cell types basal cell and secretory epithelium which differ immunohistochemically: Keratins from human stratum corneum are exclusively demonstrable in the basal cells, the keratins 8 and 18 only in the secretory epithelium. For keratin 7, 19 and the antibody "AE1 and AE3" both cell types are positive. Keratin 7 is demonstrable only focally. The secretory epithelium partly co-exprimates keratins and vimentin. Prostatic carcinomas of different grades virtually contain no keratins from stratum corneum. All other keratins are found in variable extension in the vast majority of the tumors independent of the differentiation. Vimentin is positive mostly focally in about 50% of the tumors. Prostatic carcinoma and the secretory epithelium of the prostate glands share identical immunohistochemical features and differ from the basal cell by several markers. This indicates that prostatic carcinoma rather derives directly from the secretory epithelium than from the basal cell.