Prophylaxis of alcohol withdrawal syndrome (AWS) in alcohol-dependent patients shortens the duration of stay in the intensive care unit (ICU). The objective of this study was to assess the effect of four different prophylactic regimens on the duration of ICU stay, prevention of AWS and rate of major intercurrent complications in alcohol-dependent patients admitted to the ICU after tumour resection. A total of 197 alcohol-dependent patients, diagnosed by the Diagnostic and Statistical Manual of Mental Disorders (third revised edition) with a daily ethanol intake of 60 g, were allocated randomly to one of the following regimens which were commenced on admission to the ICU: flunitrazepam-clonidine, chlormethiazole-haloperidol, flunitrazepam-haloperidol or ethanol. The duration of ICU stay, prevention of AWS, incidence of tracheobronchitis and major intercurrent complications such as pneumonia, sepsis, cardiac disorders, bleeding disorders and death were documented. On admission, patients did not differ significantly in age, APACHE II and multiple organ failure scores. ICU stay, incidence of AWS, severity of AWS (revised clinical institute withdrawal assessment for alcohol scale > 20) and major intercurrent complication rate did not differ significantly between groups. Although there was no advantage in any of the four regimens with respect to the primary outcome measures, pulmonary and cardiac patients were not included in the study. Patients in the chlormethiazole-haloperidol group had a significantly increased incidence of tracheobronchitis (P = 0.0023), probably because of an increased incidence of hypersecretion.