1. Erythrocyte aldehyde dehydrogenase activity was assayed in actively drinking alcoholics, patients with alcoholic liver disease who claimed to be abstaining, patients with non-alcoholic liver disorders and normal controls. Hepatic cytosolic aldehyde dehydrogenase was also assayed in the majority of the subjects.
2. Actively drinking alcoholics had significantly lower erythrocyte aldehyde dehydrogenase activity than controls (P < 0.01) but abstaining alcoholic liver disease and non-alcoholic liver disorder subjects did not.
3. There was a significant correlation between erythrocyte and hepatic cytosolic aldehyde dehydrogenase activity in the control group (r = 0.94, P < 0.05) but not in the other study groups.