A total of 17 methanol extracts and nine essential oils of Malaysian plants were investigated for their larvicidal activity against Aedes aegypti. Acute mortality of the fourth instar larvae was determined according to the standard WHO method. Among the samples studied, the essential oils of Cinnamomum impressicostatum Kosterm., C. microphyllum Ridl. and Curcuma domestica Valeton showed significant effects with LC 50 values of 13.7, 20.6 and 20.9 mg/ml, respectively. Except for Zingiber cassumunar Roxb., the essential oils of the other species were also effective against the larvae with LC 50 values less than 200 mg/ml. Of the methanol extracts, Garcinia praniana King, G. griffithii T. Anders, Labisia pumila var. alata Lindl., L. pumila var. pumila and Mitragyna speciosa Korth. showed relatively high activity with LC 50 values ranging from 103-271 mg/ml. The methanol extracts were generally less effective than the essential oils with most extracts exhibiting LC 50 values greater than 500 mg/ml. Pharmaceutical Biology Downloaded from informahealthcare.com by Emory University on 08/07/15For personal use only.