Eighteen plant species showing herbicidal activities were selected from secondary data. There were Murraya paniculata (L.) Jack. leaf, Hydrocotyle umbellata L. leaf, Mammea siamensis T. Anders. seed, Duranta erecta L. leaf, Pluchea indica Less. leaf, Aglaia Odorata Lour. leaf, Leucaena leucocephala de wit. leaf, Ipomoea aguatica Forsk, Eucalyptus camaldulensis Dehnh leaf, Leea macrophylla Roxb.ex Hornem. leaf, Metha cordifolia Opiz. leaf, Casuarina junghohniana Mfg. leaf, Stemona curtisii. Hook.F. root, Cassis fistula Linn. pod, Tinospora crispa (L.) Miers ex Hook.f. & Thoms. stem, Brachiaria mutica (Forsk.) Stapf leaf, Raphanus sativus var. longipinnatus L. root and Zollingeria dongnaiensis Pierre leaf.