Fourth instar larvae of Culex pipiens were exposed to six benzyl-1,3-benzodioxole derivatives to assess the effectiveness of these compounds as anti-juvenile hormone agents. Mortality ranging from between 18 and 99% was observed in larvae and early pupae but the surviving adults showed no clearly defined anti-juvenile hormone effects. Adult effects included a reduction in number of eggs developed and the presence of degenerating eggs 4 days after the blood meal.