Random-digit dialing over a period of 11 days in December 2001 yielded a total of 22,399 phone calls, from which a final sample of 502 respondents ages 18-29 emerged. Overall, 11.2 percent of the sample reported having driven within an hour of using cannabis at least once in their lifetime, and 7.4 percent had done so within the previous 12 months. Males (15 percent) were more likely than females (8.2 percent) to have driven within an hour of using cannabis in their lifetime, and in the last 12 months 10.5 percent of males and 5 percent of females had done so. Among those who reported using cannabis weekly or more often in the previous 12 months, 53.8 percent reported engaging in DUIC in their lifetime, and 40.6 percent reported DUIC in the previous 12 months. Although only 1.8 percent of the sample had driven within an hour of using both cannabis and alcohol together in the previous 12 months, this involved 6.9 percent of all recent cannabis users and 24.3 percent of those who had driven under the influence of cannabis in the previous 12 months. The prevalence of DUIC alone and in combination with alcohol is apparently low among the population examined, but is higher among those who regularly use cannabis. There may be value in education and public-health campaigns that target people who regularly use cannabis. Research should continue into the causal relationship between cannabis use and road accidents. 1 table and 26 references