Randomization will be done using a permuted block randomization system, and will be stratified by clozapine/olanzapine treatment at baseline. Treatment assignment order is random within each block, and the total number of patients assigned to each treatment is equal. The block sizes will vary between sizes 2 and 4 in random sequence. The unblinded pharmacist will be notified of the treatment assignment, and will inform unblinded pharmacists at the other sites about which study medication to dispense. In an emergency, research staff will be able to contact the pharmacy for unblinding. Rimonabant will be available in 20 mg capsules with matched placebo.