This study examined the incidence of alcohol and drugs in a sample of seriously injured motor vehicle collision victims, and differences related to pre-crash use of alcohol and/or other drugs on demographic variables, injury severity measures, and crash variables. The sample selected were all motor vehicle collision admissions to the Regional Trauma Unit at the Sunnybrook Health Science Centre in Toronto, Ontario, over a 37-month period (N = 854). Prospective demographic and injury-related information were collected from hospital charts, and crash data were collected from motor vehicle collision police reports. Blood samples were routinely collected on admission and tested for blood alcohol concentration (BAC). We found 32.0% of the BAC-tested motor vehicle collision admissions and 35.5% of drivers tested positive for blood alcohol. The drivers' mean BAC on admission was found to be 145.2 mg/100 ml, and the mean estimated BAC at crash time was 181 mg/100 ml. Drug screens were performed on a two-year subsample (n = 474), of whom 339 were drivers. Drug screens revealed that 41.3% of drivers tested positive for other drugs in body fluids, and 16.5% were positive for alcohol in combination with other drugs. Other than alcohol, the drugs most frequently detected in the drivers were cannabinoids (13.9%), benzodiazepines (12.4%), and cocaine (5.3%). Investigation of differences on demographic, injury, and crash characteristics related to precrash use of alcohol and/or drugs yielded significant findings. In the drug screened sample we found sex, admission type, and occupant status were related to precrash alcohol use. Also, use of drugs was found to interact with admission type and mean BAC on admission. Elapsed time was found to be significantly different for BAC by other drug use, with a greater length of elapsed time found for the subjects testing other drug positive but BAC negative. We found that BAC-positive drug-screened drivers were significantly more likely to be male, involved in a single-vehicle collision, not wearing a seat belt, ejected from the vehicle, and travelling at higher speeds than BAC negative drivers. No significant differences were found between BAC and/or other drug use on injury severity measures.