A closed fumigation system containing a circulating saturated atmosphere of candidate chemosterilants (31 compounds, 26 of them analogues of tepa) was tested with thePectinophore gossypiella(Saunders). Tepa and its analogue, ethyl ester of bis(1-aziridinyl) phosphinic acid, caused a high degree of sterility in both sexes without reduction in longevity, mating, or sperm transfer of the treated insects. Exposure times for the 2 compounds were 1 and 0.5 h, respectively, at 30°C. Rapid and uniform sterilizing treatment can be achieved by fumigation in a dosed circulating system.