Erythroycte delta aminolevulinic acid dehydratase (ALAD) has been suggested as a marker for detecting recent alcohol intake. Unlike other markers, ALAD activity decreases after alcohol intake. Review of the literature suggests that the main interest in this marker is because it increases rapidly after withdrawal. The present study investigated the changes in erythrocyte ALAD and serum gamma-glutamyltransferase activities after alcohol withdrawal in 120 alcoholics. Our data showed that ALAD is less sensitive than GGT as an indicator of recent alcohol intake (56% and 84% abnormal, respectively). The increase in ALAD activity was greater between day 12 and 18 after withdrawal (11%) than between day 1 and 12 after withdrawal (5%). There were as many patients returning to normal values 12 and 18 days after withdrawal, for GGT as for ALAD. Thus, our results contradict the claim that ALAD rises rapidly after withdrawal. ALAD shows no advantage over GGT as a marker of recent alcohol intake.