Possible negative reinforcing effects of perphenazine, haloperidol and amitryptiline were studied in rhesus monkeys previously trained to avoid electric shock by responding. Responding extinguished a light associated with an intravenous drug infusion scheduled to occur 30 seconds after the light was switched on. A response occurring when the light was on switched the light off for a period of 1 minute (time-out period). a response during the infusion terminated the infusion. Under these conditions, the monkeys tolerated a large number of saline infusions. Saline was replaced by different doses of perphenazine, haloperidol and amitryptiline, each for 12 successive daily 2-hour sessions. Infusions of perphenazine (0.50-1.6 microng/kg) and to a lesser extent infusions of haloperidol (2.5 microng/kg) generated and maintained responding. Most of the infusions of amitryptiline in the dose range of 1.0 to 10.0 microng/kg were tolerated. Haloperidol and perphenazine in doses higher than 10.0 micmitryptiline (500-3000 microng/kg i.v.) had no influence on shock avoidance behavior. Positive reinforcing effects of these compounds were studied in a group of monkeys trained to respond under a 10 response fixed ratio of intravenous infusions of codeine. None of the three compounds maintained responding previously engendered by codeine.