Adulticidal activity of some Malaysian plant extracts against Aedes aegypti Linnaeus Hidayatulfathi, O., Sallehuddin, S. & Ibrahim, J. Faculty of Allied Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda A. Aziz, 50300 Kuala Lumpur, Malaysia. Abstract. The adulticidal activity of methanol extracts from three Malaysian plants namely Acorus calamus Linn., Litsea elliptica Blume and Piper aduncum Linn. against adult of Aedes aegypti (L.) were studied. Standard WHO bioassay tests were used to evaluate the effectiveness of these plant extracts. The hexane fraction from methanol extract of Acorus calamus rhizome was the most effective, exhibiting LC 50 and LC 90 values of 0.04 mgcm -2 and 0.09 mgcm -2 respectively. For L. elliptica, the methanol fraction also displayed good adulticidal property with the LC 50 and LC 90 values of 0.11 mgcm -2 and 6.08 mgcm -2 respectively. It is found that hexane fraction of the P. aduncum crude extract was the least effective among the three plants showing LC 50 and LC 90 values of 0.20 mgcm -2 and 5.32 mgcm -2 , respectively. However, although A. calamus showed lowest LC values, the LT 50 results indicated that the methanol fraction of L. elliptica was most potent extract among the extracts tested.