The 24-hour urinary carcinoembryonic antigen determinations were performed on 61 patients with different stages of bladder carcinoma. Elevated titers were found in 81 per cent of the patients with active tumors and falsely positive studies were found in 7 per cent. High stage lesions were found to have high carcinoembryonic antigen levels. Plasma carcinoembryonic antigen determinations were elevated in only 45 per cent of the patients with active tumors but further study may be warranted in advanced bladder cancer cases. The 24-hour urinary carcinoembryonic antigen measurements yield the highest percentage elevations in bladder carcinoma and further investigation is required to better define its clinical application.