Field trials were carried out in northeastern Uttar Pradesh (India) to determine the effectiveness of the aphid parasitoidTrioxys indicusSubba Rao & Sharma against the cucurbit aphidAphid gossypiiGlover onLagenaria vulgaris(bottle gourd),Luffa cylindrica(ghia torai) andCucurbita maxima(pumpkin). Two initial inoculative releases of the parasitoid with the rate of 10 mummies/m2during the first and third weeks of December decreased the population growth of the aphid onL. vulgarisandL. cylindrica.A 20 to 50% reduction of the aphid number was noticed within 15 days after the first release in the fields on the two crops. The second release of the parasitoid further reduced the population by up to 65–70%. The rate of parasitism in natural conditions (control fields) and in experimental fields (where the parasitoids were released) was found to be density-dependent except in the fields ofC. maxima.The results demonstrated the potential ofT. indicusagainstA.gossypiiin a cucurbit habitat.