Laboratory, greenhouse, and field tests were made in Florida to determine the potential of the entomogenous nematodes,Neoaplectana glaseriSteiner orNeoaplectana carpocapsaeWeiser (Mexican strain), as biological control agents for the root weevil,Diaprepes abbreviatus(L.). In the laboratory, when nematodes were applied to the soil surface at rates of 25, 250, and 2,500 per cm2, mortality of 3-mo-oldD. abbreviatuslarvae ranged from 24 to 88%.N. glaseriandN. carpocapsaehad no significant effect on neonate larvae or pupae. In the greenhouse, whenN. glaseriorN. carpocapsaewere introduced toD. abbreviatusinfested citrus seedlings, larval populations were significantly (P<0.05) reduced. In field tests, when nematodes were applied at 250 per cm2, mortality of 3-mo-oldD. abbreviatuslarvae was 35 and 65% forN. glaseriandN. carpocapsae, respectively. In laboratory, greenhouse, and field tests,N. carpocapsae(Mexican strain) was significantly (P<0.05) superior toN. glaserias a biocontrol agent forD. abbreviatuslarvae.