Two heterorhabditid entomopathogenic nematode species from the Caribbean (Heterorhabditis sp. Dl - JAM34, Heterorhabditis sp. - El Yunque) and one heterorhabditid nematode from North America (H. bacteriophora, HP88) were evaluated for their ability lo survive in soil at temperatures between 11 and 35 "C and subsequently infect and reproduce in late instar larvae of the sweet potato weevil, Cylas fortnicarius (Fabricius) (Coleoptera: Apionidae). The tolerance of the three nematode species to soil temperature appeared to be related to their climatic origin. One of the species from the Caribbean, Heterorhabditis sp. D1 strain (JAM34), was more tolerant of warmer temperatures than the North American nematode H.bacteriophora HP88 strain. HP88 was also better adapted to cooler temperatures than JAM34. Heterorhabditis sp. El Yunque, a novel species, was isolated from higher elevations (600 m) in Puerto Rico and was least tolerant to test temperatures. These data indicate that interspecific differences may occur among heterorhabditid species in their tolerance to soil temperatures. The importance of these data in developing an integrated pest management strategy for the sweet potato weevil in the Caribbean is discussed.