A botanical natural product, AkseBio2, was evaluated for its larvicidal effect against Culex pipiens under laboratory conditions. The product exhibited strong larvicidal activity and caused >90% mortalities in both the young (first-second) and the older (third-fourth) larval stages of the species at 24 h at the doses of 25 and 50 ppm. However, it was determined that the young larval stages were more susceptible to the product in comparison with the older larval stages. The results suggest that the product is promising as a larvicide against C pipiens and could be useful in the search of new larvicidal natural compounds. (C) 2004 Elsevier B.V All rights reserved.