To establish baseline data on prehospital emergencies caused by opiates during a 4-month period, a retrospective analysis of run records of the Emergency Medical System in Vienna, the capital of Austria, was conducted. During the study period, there were 308 opioid emergencies involving 240 persons, an average of 2.5 overdoses per day. Severely compromised patients were treated in 67.8% of the 308 emergencies, and 79.3% of emergencies were transported to hospital; 52.5% of the involved persons were younger than 22 years of age. Sex distribution and periodicity and frequency of emergencies differed among age groups. A subgroup of individuals involved repeatedly in emergencies was identified, partly showing temporal clustering of fatal and nonfatal overdoses. Persons involved in opiate emergencies belong to heterogenous subgroups. At a local level, research should be initiated to clarify the pattern and impact of these emergencies on overall drug abuse prevention.