A survey of the natural enemies of Rachiplusia nu and Pseudoplusia includens was carried out in soyabean crops in Rio Grande do Sul, Brazil, in 1986-88. Predators were quantified in the field and the parasitoids and pathogens were evaluated on larvae in the laboratory at 24 ? 2?C and 70 ? 10% RH. The ichneumonids Campoletis sonorensis, Casinaria plusiae, Mesochorus discitergus and Microcharops bimaculata, the braconid Cotesia grenadensis and the tachinids Voria ruralis, Patelloa similis, Euphorocera sp. and Lespesia sp. were found to be important parasitoids of larvae of the noctuids at the beginning of their establishment on soyabean crops. Copidosoma floridanum and Meteorus sp. affected larvae from February onwards. The fungus Erynia crustosa caused approx. 40-50% mortality on larvae of the pests at the Arroio Grande and Capao do Leao areas.