We investigated Solanum nigrum (seeds) and Datura stramonium (shoots) against root-knot nematodes in terms of J2 paralysis and egg hatch inhibition (methanol extract), as well as inhibition of nematode development in host roots (soil amending with either S. nigrum seeds' or D. stramonium shoots' meal). Datura stramonium was found equally effective at inhibiting motility of Meloidogyne incognita and Meloidogyne javanica (both EC 50 = 427 μ g mL-1 at 3 day), but inhibition occurred more quickly for M. incognita (1 day). Solanum nigrum was faster and more effective at inhibiting motility of M. incognita than M. javanica (EC 50 = 481 and 954 μ g mL-1 at 3 day, respectively). Datura stramonium was slower, but eventually more potent in decreasing egg hatch and cell division in M. incognita eggs, than S. nigrum. Specifically, D. stramonium significantly inhibited cell division in eggs immersed in at least 100 and 1 μ g mL-1 at Day 6 and 10, respectively. Solanum nigrum impeded cell division in un-differentiated eggs immersed in not less than 10 and 100 μ g mL-1 after days 2 and 6, respectively. Both extracts were similar in suppressing J2 exclosure but D. stramonium was effective in smaller test concentrations. Specifically, D. stramonium suppressed J2 emerging from eggs immersed in 10 μ g mL-1 at day2, and in at least 1 μ g mL-1 at day 6. Solanum nigrum significantly reduced J2 hatch from eggs immersed in a minimum of 100 μ g mL-1 at day 2 and not less than 1,000 μ g mL-1 at day 6. In pots, powdered S. nigrum seeds meal was more active than D. stramonium and the respective EC 50 females/g values for M. incognita were 1.13 and 11.4 mg g-1 of soil, respectively. The chemical composition of active extracts was determined after derivatization by GC-MS. Chemical analysis of active extracts showed the presence of fatty acids with known nematicidal activity.