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Abstract. The Japanese beetle, Popillia japonica Newman, is an introduced pest on Terceira, one of nine islands in the Azorean Archipelago. Research conducted on Terceira indicates that entomopathogenic nematodes in the families Steinemematidae and Het erorhabditidae provide good to excellent control of Japanese beetle larvae, but the species that have been evaluated are not native to the Azores. An efficacious species that is native to the archipelago might provide increased capabilities for persisting and recycling in Azorean soil and weather conditions. Surveys on the islands of Terceira and Santa Maria resulted in the isolation of two Hetero rhabditis strains (Sao Mateus and Praia Formosa) with good larvicidal activity for P. japonica. Initial bioassays conducted with Steinernema glaseri (Steiner) originally from North Carolina against P. japonica third instar larvae and pupae produced LC50 values of 3.2 x 105 infectivejuveniles (IJs)/m2 and 0.9 x 105 IJs/m2, respectively. Comparative bioassays of the native isolates and S. glaseri against P. japonica revealed similar larvicidal activity. The LC5os of the Sao Mateus and Praia Formosa isolates against third instar larvae were 3.64 x 105 and 4.44 x 105 IJs/m2, respectively. The LC50 of S. glaseri ranged from 3.2 to 5.5 x 105 IJs/m2. The higher larvicidal activity of the Azorean Heterorhabditis isolates for P. japonica indicates that native nematodes are as effective as S. gla seri. Heterorhabditid species also have demonstrated ability for persistence and apparent recycling under conditions where sustain able control of this introduced pest is needed. Studies comparing the dispersal behavior of the Heterorhabditis bacteriophora Poinar Sao Mateus isolate with that of S. glaseri and native and exotic strains of Steinernema carpocapsae (Weiser) revealed that the H. bacteriophora isolate demonstrated a greater propensity to disperse than other strains in the presence or absence of P. japonica lar vae. In the presence of a host, a greater proportion of H. bacteriophora and S. glaseri dispersed than either of the two S. carpocapsae strains.