Non-target organisms killed by SWASS pellets, a bait toxicant system for screwworms,Cochliomyia hominivorax(Coquerel), were determined. Collections of insects were made at 391 sites in 19 study areas in Texas, New Mexico, Arizona, and Mexico. The reaction of domestic animals to the pellets was recorded, and pellet-baited small mammal traps were set in selected areas. Diptera comprised 93.5% of the insects collected, and 88.5% of these were Calliphoridae, Sarcophagidae, Anthomyiidae, and Muscidae. The predominant species in these families in order of abundance wereC. macellaria(Fabricius),Ravinia effrenata(Walker),Hylemya cinerella(Fallen), andSynthesiomyia nudiseta(Wulp). Mammals caught in traps includedNeotoma micropusBaird,N. Albigula(Hartley),Spermophilus mexicanus(Erxleben), andSylvilagus floridanus(Allen). Domestic animals have little or no interest in the pellet as food. On the average, ca. 10% of all pellets were degraded or removed from a site within one wk.