The objectives of this study are to examine the influence of different parasitoid host ratios [R] on the rate of parasitism [N sub(p)] and search rate [a] of the aphid parasitoid Binodoxys indicus (Subba Rao & Sharma 1958) on the host species Aphis gossypii Glover 1877. If 1, 2, 4, 8, or 12 female parasitoids [FF] were daily released per cage on 200 almost L sub(3) nymphs of the host for 4 consecutive days, the number as well as the proportion of parasitised host individuals increased. The rate of multiplication, however, [R sub(m), defined as the contribution of individual FF when more than 1 F simultaneously exploited the host patch] as well as the the search rate [a] decreased with the increase of R. Different mathematical models are given to explain the relationship between N sub(p), R sub(m), a with R. Various aspects of the behavior of the F which could give rise to interference effects are discussed. The data also furnished an insight into the number of parasitoids needed to regulate the estimated aphid population. none