Laboratory experiments were carried out at 25~2?C and 60~2% RH to determine the efficiency of the braconid Chelonus blackburni and the encyrtid Copidosoma koehleri as parasitoids of the gelechiid Phthorimaea operculella. When the individual parasitoid species were compared with the combination of both species, C. blackburni was most efficient both alone and in combination with C. koehleri, C. koehleri alone was least efficient. In combination treatments, C. blackburni reduced the survival of C. koehleri but not vice versa. The longevity of adults of C. blackburni and C. koehleri was markedly reduced in combination treatments and the number of viable cocoons was a maximum when only C. blackburni or C. koehleri was present. none