A preliminary survey on allelopathic plants found in Southeast Asia including Vietnam was carried out during 2000-2002. Nineteen species consisting of weeds, shrubs and trees were selected for their effects on bioassays. Some of these plants have been traditionally used by Vietnamese farmers as field manures and mulches. The allelopathic potential of these plants was elucidated by evaluating the inhibitory exhibition from their leaves, stem and root on germination and growth of radish. The three species showing the greatest allelopathic potential were Galactia pendula, Leucaena glauca and Melia azedarach. Four other species including Desmodium rezoni, Euphobia hirta, Manihot esculenta and Morus alba were assessed to be the second most suppressive to radish germination and growth. Findings also indicated inhibitory exhibition of allelopathic plants were species dependent. Moreover, inhibitory effects varied among plant parts such as the leaves, stem and root. (C) 2003 Elsevier Science Ltd. All rights reserved.