Serum concentrations of immunoglobins IgA and IgG were determined in: Alcoholic men without liver damage (normal laboratory tests and only slight abnormalities in liver biopsy). 2. Patients at different stages of alcoholic liver disease. 3. Non alcoholic patients with liver disease. The serum IgA concentration was increased in all groups of alcoholics and this increase was related to the severity of liver damage. It was also raised in non alcoholic patients but both the degree of increase and the IgA/IgG ratio could be used to differentiate them. The increase in the serum IgA concentration in alcoholics without liver damage has not previously been proved and the reasons put forward for it in alcoholics are not valid for this group.