1. δ-Aminolaevulinic acid (ALA) dehydratase, γ-glutamyl transpeptidase (γGT) and leucine aminopeptidase (LAP) have been measured in chronic alcoholics.
2. Within 48 h of alcohol withdrawal ALA dehydratase activity was depressed in chronic alcoholics even though the blood alcohol content was zero. A second group of chronic alcoholics studied 7 days after the cessation of alcohol consumption had normal ALA dehydratase activities.
3. ALA dehydratase activity is more reliable than measurements of γGT and LAP in monitoring alcohol habits of chronic alcoholics.