SWASS a bait-toxicant system for the screwworm, Cochliomyia hominivorax (Coquerel), was evaluated on the island of Curacao, Netherlands Antilles. The SWASS Units (individual components of the screwworm adult suppression system) were dispersed (10–20/km2) by air over the rural part of the island and by ground (10–20/km2) within its urban areas for a period of ca. 15 wk from Feb. 26-May 13, 1977. Collection of adults in survey traps indicated a 65–85% suppression. Reported larval incidence declined 30–70% from that expected. There was an increase in the proportion of males captured in the traps during the period that SWASS units were in the field which reflected the 1♂ :5 ♀ kill ratio that is characteristic of SWASS. In mid-May, the distribution of SWASS units was discontinued, and releases of sterile screwworm flies (1575/km2) were initiated. The releases reduced the residual population of the screwworms on Curacao to insignificant numbers in 3–4 wk, and the island was declared screwworm free on Oct. 25, 1977, when over 3 mo had passed without an infested animal being reported.