Carcinoembryonic antigen (CEA), described by Gold and Freedman, was the first fetal tumor antigen isolated in tumor homogenates. The present study investigated the biological behaviour of CEA in superficial transitional cell carcinoma of the bladder, deep localized and disseminated. The study comprised 100 subjects; 30 carefully-selected healthy subjects comprised the first group and 70 patients with a diagnosed transitional cell carcinoma of the bladder comprised the second group. Serum CEA was determined by enzyme immunoassay (CEA, EIA, Roche). Our results suggest that serum CEA determination affords no diagnostic benefit in this type of malignant tumor.