In 1977 and 1978 the serum concentration of alpha-1-fetoprotein (AFP) in 3200 patients was measured for diagnostic purposes. Values above 320 ng/ml were observed in 75 patients; they underwent closer study. The final diagnoses were hepatoma (50), germ cell tumors (15), other malignant tumors (6) and acute hepatitis (4). Also, chronic hepatitis and liver coma may be associated with AFP values above 320 ng/ml. Repeated measurements usually provide further diagnostic information.