The major parasites of cabbage looper larvae in California cotton areHyposoter exiguae(Viereck),Microplitis brassicaeMuesebeck, andCopidosoma truncatellum(Dahlman). Parasitization for a given species was greater when the species occurred alone than when it occurred in combination with one or two other species. However, total parasitization did not decrease with an increase in number of parasite species. Implications for multiple-species introductions are discussed.