SUMMARYA study was made of the effects of concentrations of 2 to 32 ppm of oximecarbamate, organophosphate and benzimidazole nematicides on the hatch, larval viability and migration ofMeloidogyne javanica, M. incognitaandM. haplaand on development ofM. javanicain roots. Aldicarb at less than 8 ppm had little effect on hatch and methomyl markedly affected only the hatch ofM. hapla.As little as 2 ppm of fenamiphos or thionazin markedly reduced hatch of all three species but less than 8 ppm ethoprophos significantly reduced only the hatch ofM. incognitaand phorate had little effect on hatch. Benomyl and thiabendazole had no significant effects on hatch. When egg masses ofM. incognitawere transferred from nematicides which suppressed hatch to water, hatching occurred, but aldicarb, fenamiphos, ethoprophos and thionazin significantly reduced total hatch.None of the nematicides killed larvae of the three species immersed in 16 and 32 ppm solutions of them for 3 days. Aldicarb at 2 ppm reduced migrations of all three species; the effects of methomyl, fenamiphos or thionazin on migration varied according to species, while phorate, ethoprophos, benomyl or thiabendazole had little or no effect on migration. Aldicarb or thionazin at 2 ppm stopped development ofM. javanicain roots of tomato seedlings while methomyl, ethoprophos or fenamiphos at 4 ppm reduced development by 60% and at 8 ppm of ethoprophos or fenamiphos or 16 ppm of methomyl, development was stopped. Phorate had little effect on development and benomyl or thiabendazole had no effect. Nematicide concentrations which reduced development prevented the normal orientation of larvae in the roots and reduced or prevented giant cell formation.