Aims. To characterize the population of drug users consulting the Emergency Room (ER) of a university hospital with acute opiate overdose (AOO) and to assess rate of referral to specialized treatment programme. Design. Survey of a 12-month sample of AOO patients. Measurements. Medical and psychosocial features of the drug users, details of emergency treatment and referral by a mobile resuscitation team (SMUR) and the ER of our hospital (CHUV-Lausanne, Switzerland). In addition fatal AOO cases were collected by the Institute of Forensic Medicine (IFM) during the same period. Findings. One hundred and eighty-four cases of AOO (134 patients) were treated. The files of the IFM detailed six additional deceased cases. This population of drug users was characterized by an over-representation of men (73%), by young age (27.4 years), by a high rate of multi-drugs use (90%) and by a high rate of multiple previous overdoses (2.6). Average length of stay was 20.1 hours but 41% of cases stayed less than 8 hours. Only one patient was readmitted within an 8-hour period. When discharged, 78% returned home. Unexpectedly, 67% of patients were not referred to any therapeutic programme for drug addiction. Conclusion. This study shows the low mortality of AOO when treated but also demonstrates the need to improve psychosocial evaluation and referral of drug addicts admitted with AOO.