4. Subjects with daily marijuana use will be excluded because of the possibility of physical dependence on cannabis. Those with with marijuana use no more than once a week will not be excluded because such subjects will not be physically dependent on marijuana and so not at risk for rimonabant-elicited acute cannabis withdrawal. Experimental studies of human cannabis physical dependence and withdrawal suggest that high-dose, multiple times a day administration is needed to produce physical dependence (Jones et al., 1976; Haney et al., 1999)