In laboratory bioassays, Steinernema riobrave Cabanillas, Poinar and Raulston (355 strain), Steinernema carpocapsae (Weiser) (Mexican 33 strain), Steinernemafeltiae (Filipjev) (UK76 strain), and Heterorhabditis bacteriophora Poinar (HP88 strain) were all capable of infecting and killing three termite species, Heterotermes aureus (Snyder), Gnathamitermes perplexus (Banks), and Reticulitermes flavipes (Kollar) in laboratory sand assays. S. riobrave and S. feltiae caused low levels of Reticulitermes virginicus (Banks) mortality under the same conditions. At 22 degrees C, significant mortality (> or = 80%) of worker H. aureus and G. perplexus was caused by S. riobrave, in sand assays, indicating the need for further study. Because of the short assay time (3 d maximum), reproduction of the nematodes in the target host species was not recorded. All nematode species were observed to develop to fourth-stage juveniles, preadult stages, or adults in all termite species with the exception of R. virginicus. Only S. riobrave developed in R. virginicus. Nematode concentration and incubation time had significant effects on the mortality of worker H. aureus. S. riobrave consistently generated the highest infection levels and mortality of H. aureus in sand assays.