Laboratory and field tests were conducted to determine the attractiveness of the insect growth regulator methoprene to ovipositing mosquitoes when presented at concentrations used in mosquito control programs. Laboratory experiments indicated that ovipositing Culex quinquefasciatus and Aedes aegypti were not attracted to methoprene. In field experiments, Culex stigmatosoma and Cx. quinquefasciatus larval dip counts in experimental ponds treated with methoprene briquets were not significantly different from untreated control ponds. Water taken from these methoprene-treated ponds was not attractive when compared with water taken from untreated ponds to ovipositing Cx. quinquefasciatus in laboratory experiments. These studies provide strong evidence that methoprene is not attractive to ovipositing mosquitoes at concentrations within the range of field applications.