Responding by three squirrel monkeys was maintained under multiple-and single-component 5-minute fixed-interval (FI) schedules of either food or electric shock presentation. Under the multiple schedule, a response after 5 minutes had elapsed produced either food or shock depending on the prevailing stimulus conditions; single-component FI schedules maintained responding either by food or shock presentation alone. Responding under either the food or the shock schedules was positively accelerated throughout each FI. During certain phases of the experiment, overall response rates maintained by foor were comparable to those maintained by shock. Alcohol (1.0-3.0 g/kg), chlordiazepoxide (1.0-10.0 mg/kg) and pentobarbital (1.0-10.0 mg/kg) increased responding maintained by food but decreased responding maintained by shock. These effects were obtained under both the multiple- and single-component schedules. Low to intermediate doses of cocaine (0.1-1.0 mg/kg) increased responding maintained by either food or shock, whereas higher doses (3.0 mg/kg) generally decreased responding under these conditions. The effects of chlordiazepoxide were also studied with one monkey when response rates maintained by food or shock were equal, when rates of food-maintained responding were lower than those maintained by shock and, finally, when rates of responding maintained by food were higher than those maintained by shock. Under all of these conditions, chlordiazepoxide increased food-maintained response rates and decreased responding maintained by shock presentation.