Serum Gm polymorphism was studied in 69 patients with liver cirrhosis, in 64 with liver cirrhosis plus hepatoma, in 40 with hepatoma without evidence of cirrhosis, and in 256 controls. The distribution of Gm factors in liver patients differed from that in the control group, this difference apparently being due to the distribution in cirrhosis patients negative for HBsAg and anti-HBs. Furthermore, significantly more heterozygous Gm individuals were found in this group of patients than in the control group. Thus it appears that Gm heterozygous individuals are prone to develop cryptogenic cirrhosis under the influence of other, as yet undetermined factors.