Drug-driving behaviour among out-of-treatment dependent drug users has not been investigated while a theoretical perspective on the propensity of certain drug users to drive while impaired has not been suggested. This paper examines illicit drugs and driving behaviour and accident involvement among out-of-treatment current drug users. Psychological evidence of belief-based mechanisms to account for the decision to drive while impaired by drugs are provided. A total of 210 out-of-treatment current drug users were interviewed in a non-clinical setting by privileged access interviewers. Questionnaire measures were: current illicit drug use, severity of dependence, illicit drugs and driving behaviour, impaired and unimpaired accident involvement and beliefs and perceptions about the impairing effects of a number of illicit drugs. Analyses are restricted to participants who reported driving during the previous 12 months (n = 71). Fifty-eight participants (81.7%) reported driving immediately after consuming illicit drugs, primarily heroin and cannabis. Of these 41.4% (n = 24) had at least one road accident as a driver, 15 of whom (62.4%) reported accident involvement following recent drug consumption. Belief-based results showed that participants who reported never driving after using illicit drugs perceived heroin, methadone and alcohol to be greater significance for accident risk and driving skills impairment than other drugs. Those drivers who reported drugs and driving behaviour believed only alcohol to be significantly more impairing than other drugs. Findings indicated that illicit drugs and driving behaviour is common among out-of-treatment drug users. Accident involvement among this cohort is characterised by the previous consumption of illicit substances. Differential beliefs about the effects of drugs on driving performance and accident risk were shown to be dependent upon frequency of drugs and driving behaviour. Results are discussed in terms of experiential factors and consistency theories of attitude formation and change.