Bell peppers (Capsicum annuum L,) are classified as nonclimacteric fruits while some hot peppers have been reported as climacteric. Responses of peppers to exogenously applied ethylene-releasing compounds suggest ethylene involvement in the ripening process. Ethylene production and respiration rates in 13 cultivars of pepper: 'Camelot', 'Cherry Bomb', 'Chiltepin', 'Cubanelte', 'Banana Supreme', 'Habanero', 'Hungarian Wax', 'Mesilla', 'Mitla', 'Savory', 'Sure Fire', 'Tabasco', and 'King Arthur' were studied under greenhouse and field conditions. Fruit from each cultivar were harvested at different maturity stages determined by color, ranging from mature-green to full red-ripe. Carbon dioxide and ethylene production mere measured by gas chromatography. Both variables were significantly different among maturity stages for all cultivars, Respiration rates were between 16.5 and 440.3 mg.kg(-1.)h(-1) CO2, Ethylene production ranged from 0.002 to 1.1 mu L.kg(-1).h(-1). Two patterns of CO2 production were identified: higher CO2 production for mature-green fruit with successive decreases for the rest of the maturity stages or lower respiration rates for mature-green fruit with an increase in CO2 production either when fruit were changing color or once fruit were almost totally red. A rise in CO2 production aas present for most cultivars, Ethylene evolution increased significantly at maturity or before maturity in all cultivars except 'Cubanelle' and 'Hungarian Wax'. Respiration rates and ethylene production were significantly different among cultivars at the mature-green and red stages.