To evaluate the histological and immunohistochemical characteristics of ectopic prostatic tissue. We studied 20 cases of ectopic prostate. In 85% (17/20) of the cases, the ectopic prostatic tissue was located in the bladder; in the remaining cases, it was located in the urethra. In 60% of the cases (12/20), no significant inflammatory or reactive/reparative changes were identified in the adjacent tissue. Immunohistochemical stains for prostate-specific antigen, prostate-specific acid phosphatase, and prostein were positive in the glandular epithelial cells of all cases. Stains for 34βE12 and p63 confirmed the presence of basal cells in all cases. There was no overexpression of α-methylacyl-CoA racemase in any of the cases. There was cytoplasmic luminal staining for CD10 and cytoplasmic staining for cytokeratin 18 in acinar cells in all cases. In cases in which followup data were available, no patient was found to have residual or recurrent ectopic prostatic tissue and none developed prostatic adenocarcinoma. Ectopic prostatic tissue is occasionally encountered in the lower urinary tract, most commonly in the bladder and urethra of males. Ectopic prostatic tissue has histological and immunohistochemical characteristics that are indistinguishable from those of normal prostatic tissue, and most likely represents the persistence of embryonic structures. © 2011 Blackwell Publishing Limited.