Nematicidal activity of eight essential oil components; trans-anethole, anis alcohol, p-anisaldehyde, benzaldehyde, 4- methoxyphenol,trans-cinnamaldehyde,(R)-(C)-pulegone,2-furaldehyde,and a non-essentialoil component anisole, was tested against the root-knot nematode Meloidogyne javanica in solutions in 200-ml and 3-l pots and in microplots. Among the anisole derivatives, p-anisaldehyde showed the highest nematicidal activity in solutions and in soil. However, trans-cinnamaldehyde, 2-furaldehyde and benzaldehyde showed higher nematicidal activity than p-anisaldehyde in the 3-l pot experiments.EC50 values of trans-cinnamaldehyde for juvenile immobilisation and hatching inhibition in vitro were as low as 15 and 11.3 ¹l/l, respectively. In the 3-l pot experiments, trans-cinnamaldehyde, 2-furaldehyde, benzaldehyde and carvacrol at a concentration of 100 mg/kg greatly reduced the root galling of tomato, whereas trans-anethole was not effective. In a microplot experiment, soil treatment with trans-cinnamaldehyde (50 ml/m2 ) reduced the galling index and increased the shoot weight of tomato plants. Although further experiments, such as development of formulations and application methods, are needed, some essential oil components, especially aldehydes, can be developed into lowtoxicity nematicides.