Plasma and urinary CEA levels in patients presenting with haematuria have been studied to assess whether they facilitate the differentiation between benign and malignant urothelial conditions. Plasma CEA is of no diagnostic value although, if raised, it may suggest an invasive tumour. Urinary CEA levels are only of value in the absence of urinary infection; even then, only 37% of the cases with overt urothelial tumours had raised titres. A knowledge of the urinary CEA level, therefore, would seem to contribute little to the diagnosis of patients presenting with haematuria and all patients must still be investigated by the conventional techniques of urinary bacteriology, cytology, intravenous pyelography and cystourethroscopy.