Experimental Design and Methods: Experiment I: In this within-subject, randomized, double-blind, dose-escalation study, six participants receive 7 days of THC (40-120 mg/day). On Day 8, five participants receive 20 mg rimonabant; one receives placebo. If withdrawal criteria (greater than or equal to 150% or 2.5-fold increase in selected visual-analog scales) are not met in all five participants receiving rimonabant, separate groups of six are similarly treated with 40, 60 or 80 mg rimonabant, if necessary. The PI and MRP will submit all adverse events and relevant cardiovascular and scientific data to the IRB at the completion of each rimonabant dose panel. When the extramural NIDA DSMB is in place, it will review all data collected to date and develop and implement a monitoring plan, including review on completion of each dose cohort. DSMB recommendations will be reviewed by the Sponsor, Clinical Director and IRB before proceeding to the next dose cohort. In addition, if any subject has an intolerable adverse event (ie, an adverse event leading to study discontinuation) or serious adverse event in response to rimonabant on Day 8, the blind for that subject will be broken, and a report sent to the Sponsor, the extramural NIDA DSMB when in place and the IRB for discussion.