Embryos of the primary screwworm, Cochliomyia hominivorax (Coquerel), were successfully permeabilized for use in subsequent cryopreservation studies. Mortality was greater for eggs incubated for\u3c5 h before treatment. The mean survival of embryos to first instars was 55.7, 61.1, and 62.6% when the embryos were incubated for 5, 5.5, and 6 h before treatment, respectively. The survival to the pupal and adult stages was low. An improved media for culturing the embryos during and immediately after treatment needs to be devised and the procedure for rearing the larval stages also needs to be altered to improve survival for emerging adults