We report on a rare primary undifferentiated carcinoma of the bladder producing alpha-fetoprotein in a woman. Definitive features included an aggressive, invasive and rapidly growing tumor with a hepatoid carcinomatous lesion on histological examination. Histopathological findings suggested that the multipotent transitional cell induces production of alpha-fetoprotein. The association of an aggressive tumor with the ability to produce this antigen suggests a possible benefit in measuring serum alpha-fetoprotein levels and examining histological sections for its expression in primary undifferentiated carcinoma of the bladder. Further study may indicate radical cystectomy when the resected specimen produces alpha-fetoprotein, particularly if tumors appear to be aggressive and highly vascularized as in our case.