BACKGROUND: While there is substantial support in the literature for an increased prevalence of cannabis use in cigarette smokers, emerging studies allude to the possibility that cannabis users may, in turn, be at significantly elevated risk for rapid transitions in their cigarette smoking trajectories. If there is evidence in its favor, the increased rates of cigarette smoking in cannabis users may prove to be the most significant public health problem associated with cannabis use. METHODS: In a sample of 3787 female twins (age range 18-29 years), we examined, using discrete-time survival analyses, whether women who reported cannabis use were at increased risk for regular cigarette smoking and progression to nicotine dependence. RESULTS: After controlling for a large number of potential covariates, we found that women who used cannabis were at 4.4 and 2.8 increased hazards for transitioning from initiation to regular smoking and from regular smoking to nicotine dependence, respectively. CONCLUSIONS: Cannabis use is associated with transitions to more involved stages of cigarette smoking in women. This is a source of public health concern, first due to the high mortality associated with cigarette smoking and second, due to the high prevalence of cannabis use in the general population.