Ten interviewers questioned a sample of 615 male truck drivers on their amphetamine and alcohol usage at eight road houses known to be frequented by truck drivers on major New South Wales highways. After verifying consistency of responses to questions on alcohol and amphetamine use, an analysis of the data revealed no significant relationship between alcohol use and accident involvement, but there was a significant relationship between amphetamine use and accidents. However, it is possible that the amphetamine use and accident involvement correlation may be spurious due to the relationship between number of hours behind the wheel and accident frequency. Therefore, the link between amphetamine use and variables indicating fatigue suggest that drivers may be at risk if too much reliance is placed on drugs to maintain alertness, which can dissipate without warning and precipitate sudden, severe fatigue. Other data show significant relationships between amphetamine use and number of hours worked per week, mileage, and recreation (drug users tended to have no time for leisure activities). Financial worry may also contribute to long hours and is significantly related to both alcohol and amphetamine use. Other correlations between aggression and alcohol and amphetamine use suggest that drivers using these substances may not cope well with the vicissitudes of traffic situations. It is concluded that correlations between drug use and other variables suggest hazardous driving behavior. Because truck drivers are not convinced about the relationship between 'pep pills' and dangerous driving, it is urged that publicity on the deleterious effects of amphetamines be worded carefully to discredit driver opinions that these drugs are necessary insurance against falling asleep at the wheel. Eleven references and seven data tables are provided.