Potentiality of the aphid parasitoid species, Lysiphlebus testaceipes (Cresson) (Hymenoptera: Aphidiidae) against three species of aphids was studied. All biological studies of the parasitoid on its host, Rhopalosiphum padi (L.) were also studied under laboratory conditions. Developmental periods were estimated on R. pad/~ Aphis craccivora Koch. and Schizaphis graminum Rand .. Number of ovarian eggs, total number of eggs laid and number of mummies/ female of L testaceipes when parasitized R. padi 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. padi was faster than that of its parasitoid on R. padi. Host preference indicated that the parasitoid preferred S. graminum, followed by R. padi and then A. craccivora