Parasitism rates were analyzed forHelicoverpa armigerafeeding on four different crops in western Tanzania (1982–1985), during a period in which all crops were inhabited by the insect. The major parasitoid species differed markedly in their crop associations, withPalexorista laxa,Apanteles diparopsidis, andChelonus curvimaculatusstrongly associated with sorghum,Cardiochilesspp. mostly associated with cotton, andCharopssp., mostly associated with the weed–cropCleomesp. ForP. laxa,Cardiochilesspp., andCharopssp., the crop effect explained about 50% of the variance in parasitism among crop, month, and year. This was less forA. diparopsidisandChelonus curvimaculatus, which were erratic in their occurrence from year to year. Implications of parasitoid–crop associations for biological control ofH. armigeraare discussed.