Nematicidal activities of leaf or root extracts of four selected medicinal plants (Azaddirachta indica L., Moringa oleifera L., Lantana camara L., and Glycyrrhiza glabra L.) were tested against the larvae of the root-knot nematode; Meloidogyne spp. Leaves of each of A. indica, M. oleifera, and L. camara and roots of G. glabra were air-dried, grinded then extracted by the appropriate organic solvent. The nematode juveniles were exposed to these extracts at concentrations 500, 1000, 2000, 4000 ppm for 24, 48 or 72 hs. A. indica extract was the most effective in increasing larval mortality, followed by M. oleifera extract. There was a gradual increase in larval mortality with increasing the extract concentration and the duration of exposure. Being the most effective, the crude extract of A. indica was analyzed for the effective ingredients by using GC/MS. The active chemical constituents were Hexane, 2, 4-dimethyl; Hexane, 2,2,5-trimethyl-;Cyclohexane, 2,4-diethyl-1-methyl-; Methylbicyclo[4.2.0] Octane; Methallylcyclohexane; Cyclohexane ethyl-; Heptane, 2,6-dimethyl; Cyclohexane, 1,2,4-trimethyl-, (1α,2β,4β)-; Trans-1,2-Diethyl cyclopentane; Octane, 4- methyl-; Heptane, 2,3-dimethyl-; Benzene, 1,3-dimethyl-; Cyclohexane, 1,1,2-trimethyl-; Cyclopentane, 1-methyl-2-propyh-; 1-Ethyl-4- methylcyclohexane; p-Xylene; Nonane; Cyclohexane, 1-ethyl-4-methyl-, cis-; Benzene (1-methylethyl)-; Cyclohexane, propyl-; Octane, 2,6-dimethyl-; Benzene, propyl-; Heptane, 3-ethyl-2-methyl-; Benzene, 1-ethyl-2- methyl-; Benzene, 1,2,3-trimethyl-; Decane; Decane, 4-methyl-; Decane, 2-methyl, Undecane; Undecane, 2-methyl-; Dodecane; -; o-Xylene; Mesitylene; and Naphthalene, decahydro-, trans-.