Carbohydrate-deficient transferrin (CDT) is a marker of chronic alcohol abuse, which has recently been introduced to evaluate the physical fitness for obtaining a driving license. The aim of the present study was to evaluate the prevalence of elevated CDT levels in subjects stopped while driving under the influence of alcohol by using a validated method based on capillary electrophoresis. The study was carried out on a group of 40 drunken drivers (group A) and on a control group (n=51) of subjects chosen from the general population (group B). CDT was directly determined by capillary electrophoresis in free solution and UV detection at 200 nm. CDT results from both groups were classified as "negative" or "positive" on the basis of the cut-off set at 2.00% (CDT index). The subjects classified as "positive" in group A were 24 (60%), whereas in group B were 2. The subjects classified as "negative" in group A were 16 (40%), whereas in group B was 49 (96.1%). The comparison of the observed percentages, evaluated with the chi(2)-test, was highly significant (p<0.001). The present study confirms the high prevalence of chronic alcohol abusers among drunken drivers and the usefulness of CDT as a predictor of the risk of drunk driving.