This paper uses individual level data from the National Drug Strategy Household Surveys to estimate the price responsiveness of participation in cannabis, alcohol and cigarette use. In addition to own price effects, we estimate cross price effects and the impact of decriminalizing cannabis use. We find that participation is responsive to own prices. There is some evidence that cannabis is a substitute for alcohol and a complement to cigarettes, and that alcohol and cigarettes are complements. The liberalization of cannabis laws in South Australia may have led to a temporary increase in cannabis use among the over-30 age group.