Sera ofIt has been shown that chemically induced primary and transplantable hepatomas of mice and rats synthesize and secrete into the blood a specific protein of the embryonal serum, af-globulin (Abelev, 1963(Abelev, , 1965 Abelev et al., 1963a, b ; Grabar et al., 1965;Perova and Abelev, 1967). This protein which possessed distinct antigenic properties is a dominant component in the a-globulin fraction of foetal serum. It is usually discerned during embryonal and the first three weeks of neonatal life of mice and rats. It has not been detected in four week old or older animals. Synthesis of a/-globulin was found to resume in primary and transplantable hepatomas, though not in all cases. This protein could not be detected in a number of tumours of other than hepatic origin. Tatarinov (1964Tatarinov ( , 1965 has demonstrated that this phenomenon, af-globulin synthesis, takes place in patients with primary carcinoma of the liver. He suggested that this test could be used in the differential diagnosis of primary and metastatic liver tumours. He showed that the test was specific for hepatocellular tumours