Epidermal growth factor (EGF) concentration and 24-hour excretion in urine were measured with a radioimmunoassay in 18 patients previously treated for various types of urinary bladder tumors and a comparable control group of 18 normals. The median concentration of EGF in urine from the patients was 1.50 nmol/l and from normals 3.03 nmol/l. The median 24-hour excretion of EGF in urine from the patients was 1.96 nmol and from normals 3.33 nmol. These differences between patients and normals were statistically significant (p < 0.05 and p < 0.005) although there was an overlap in individual values of EGF concentration and excretion in urine from patients and normals. This study suggests that urothelial neoplasia is related to a low concentration and excretion of EGF.