Hepatoid adenocarcinoma is rare in the urinary bladder with only three well-illustrated previously reported cases. Pathological diagnosis is based on a combination of histological features resembling hepatocellular carcinoma and the positive immunostaining for alpha-fetoprotein. We present the clinicopathological features of four additional cases. The patients were males 66, 85, 61 and 68 years old. Hematuria was the initial symptom in all four patients. Two cases were treated by cystoprostatectomy and the remaining two by transurethral resection of the bladder. On histology, the cases showed a mixture of cells growing in a solid fashion and sheets or anastomosing trabeculae of hepatoid cells merging focally with a secondary glandular pattern of adenocarcinoma. Intracytoplasmic hyaline globules in all and bile production in three of the cases also supported the impression of hepatocytic differentiation. Immunoreactivity for alpha-fetoprotein, low molecular weight cytokeratin, alpha-1-antitrypsin, albumin, epithelial membrane antigen and a striking canalicular pattern when stained against polyclonal carcinoembryonic antigen (CEA), all indicate hepatocellular differentiation. The hepatic nature of the cells was further assessed by detecting the recently incorporated marker hepatocyte paraffin 1, by means of immunohistochemistry and albumin gene mRNA non-isotopic in situ hybridization, both of which had positive signals in all four cases. Three patients died 12, 14 and 19 months after diagnosis. The fourth patient was alive with disease at 26 months of follow-up. In conclusion, hepatoid adenocarcinoma seems to be an aggressive malignant neoplasm that is rare in the bladder whose correct diagnosis may need appropriate immunohistochemical and in situ hybridization means in addition to a complete patient clinical and pathological evaluation. The exact histogenesis and classification of these tumors remains to be established.