The effects of superparasitism on the size, rate of development, progeny production, sex ratio and percentage parasitism of the parasitoid Pediobius furvus (Gah.) and the number of parasitized hosts producing mature parasitoids were investigated. High parasitoid egg densities in hosts were obtained using two host densities (1 and 2) and three arbitrary parasitoid densities (1, 2 and 5) under two exposure times (12 and 24 h). Superparasitism in P. furvus resulted in a reduction in the number of adults that matured and a reduction in the size and preponderance of male production. Dissections of the parasitized host pupae of the stem borer Chilo partellus (Swinhoe) showed no combat among developing wasps. Immature supernumeraries were eliminated by starvation and/or suffocation. The results showed that P. furvus larvae are not harmed by surplus food material in their hosts and that the female parasitoid preferred to lay more eggs into unparasitized than into parasitized host pupae.