Screwworms, Cochliomyia hominivorax (Fig. 1), have been eradicated from the USA and now have a tenuous hold only in the Yucatan peninsula of Mexico, where control programmes based on massive release of sterile males have recently been initiated. Sterile male release operations are now underway in Guatemala and proposals have been made to extend the eradication procedures south to the Darien Gap in Panama. It is planned to extend the barrier zone to Belize and Guatemala later this year. This article reviews the progress and operational obstacles of the screwworm eradication programme.