The effects of the nematocides Aldicarb (Temik 10G), Aldoxycarb (Standak 75 PM) and DBCP (1,2-dibromo-3-chloropropane, Fumazone 86 E) on control of plant-parasitic nematodes and yield of a 7 yr old banana (M. acuminata AAA, cv. Giant Cavendish) plantation, were studied in Guacimo, Costa Rica. The results of a 24 mo. root sampling revealed that the chemicals caused a significant reduction of Radopholus and Helicotylenchus populations when compared to a control without nematocidal treatment. The most efficient product was Aldicarb, at rates of 3 and 6 g a.i./unit of production (the mother plant and its descendants). This product, at 3 g a.i./unit of production, also gave the best results regarding number of bunches and yield. There were no significant differences among treatments in the weight and the ripening period of the bunches or in the number of hands/bunch. DBCP was effective for control of nematodes but not for other variables. Aldoxicarb, at 9 g a.i./unit of production, significantly increased the pseudostem diameter and was as effective as DBCP for control of nematodes. The yield increases caused by the nematocides during a 21 mo. period were related to the number but not to the quality of the bunches.