Alcohol and illicit drug abuse are major health care problems frequently leading to emergency department admission. The aims of this survey were (1) to determine for the Ghent University Hospital how frequently substance abuse contributed to emergency department admissions, (2) to describe the most important clinical features of these patients and (3) to determine how frequently these patients were referred to appropriate psychiatric services. All 1,941 patients attending the emergency department during the month of September 2003 were registered by the attending emergency department personnel. After exclusion of 8 cases, 1,933 patients were included: 198 (10%) with substance abuse leading to the emergency department admission (= INTOX group) and 1,735 (90%) in the NON-INTOX group. Males and the 21-50 years age group were overrepresented in the INTOX group. Patients with substance abuse were also overrepresented during the night, but not during the weekend. Among the patients from the INTOX group the most frequent reason for the emergency department visit was a psychiatric problem (102/198; 51%). Traumatic lesions related to a fight (n= 19), to a traffic accident (n= 17) and to leisure time activities (n=30) were also frequent. In most patients, only alcohol was abused (144/198; 73%), most frequently chronically (102/144; 71%). In 13% (26/198), there was only illicit drug use, and in 14% (28/198) alcohol abuse was combined with illicit drug use. Among the 54 patients with illicit drug use (with or without alcohol abuse) the most frequently reported drugs were cannabis (54%), cocaine (41%), amphetamines (39%) and opiates (39%). With regard to referral to appropriate psychosocial services it was striking that 53% (19/36) of trauma patients with chronic substance abuse were not offered that type of help. We conclude that abuse of alcohol--and to a much lesser degree illicit drugs--is a frequent cause of emergency department admissions. Our data may help to convince and/or reinforce health care policy makers, emergency department medical directors and the public that alcohol consumption (much more than illicit drugs) is responsible for avoidable morbidity and mortality, and that well-co-ordinated strategies against unhealthy alcohol use are urgently needed. In this respect, the importance of detection and referral of emergency department patients with unhealthy alcohol use should be stressed.