Potentialit:y of the aphid parasitoid species, Lysiph/ebus testaceipes (Cresson) (Hymenoptera: Aphidiidae) against three species of aphids was studied. All biological studies of the parasitoid on its host, Rhopalosiphum pad! (L.) were also studied under laboratory conditions. Developmental periods were estimated on R. pad,, Aphis cra cci vo ra Koch. and Sc/v2’aphis graminum Rond.. Number of ovarian eggs, total number of eggs laid and number of mummies! female of L. testace,pes when parasitized R. pad! were estimated as 164±41.08 and 43.85±20.22 (eggs! female) and 34.23±13.74 mummies! female, respectively. Respective percentages of adults’ emergence and sex-ratio were 61.62% and 1:1.12 (female: male). Shortest longevity was recorded when the adults were starved. Life table studies showed that the intrinsic rate of increase for R. pad! was faster than that of its parasitoid on R. pad Host preference indicated that the parasitoid preferred S. gram!num, followed by R. pad! and then A. cracc!vora.