AbstractBased on the analogy between anticancer drugs and insect chemosterliants, both of them acting by virtue of their alkylating capacity, chloromethyl carboxylates (described by Bodor and co‐workers as potential anticancer drugs of the soft alkylating agent type) including the chloromethyl ester analogues of the juvenoids hydroprene and methoprene were prepared and tested for chemosterilant and morphogenetic juvenile hormone activity. While the chloromethyl esters of some simple carboxylic acids were inactive in this respect, the juvenoid chloromethyl esters revealed both chemosterilant and morphogenetic activity against Dysdercus cingulatus comparable with that of the known juvenoids hydroprene and methoprene. At the same time their activity against Pieris brassicae showed a sharp drop compared to the ‘parent’ compounds. The results suggest a species‐dependent rate of enzymatic hydrolysis of the chloromethyl ester group as a possible reason for their selective action. Thus, the chloromethyl ester group might function as a ‘selectivity factor’).