Prostatic-type epithelium in urinary bladder. Clinical, histologic, and immunohistochemical study. Six cases of urinary bladder mucosa with prostate-type epithelium were studied clinically, morphologically, and immunohistochemically. All patients were male with an average age of fifty-three years; most presented with painless hematuria. Histologically, two types of lesions were observed, the polypoid located in various sites of the bladder wall and the flat lesion found in the bladder neck. Both lesions shared in common a prostatic-type and transitional surface epithelium while prostatic-type glands were prominent in the polypoid lesion. The prostatic-type epithelium was confirmed immunohistochemically by detection of prostatic specific antigen and prostatic acid phosphatase. Based on specific findings we considered the metaplasia as the most reliable histogenetic aspect. 