We investigated the rates of egg and larval parasitism in transgenic and non-transgenic, conventional cottons. Sentinel eggs and larvae of the cotton bollworm, CBW, Helicoverpa armigera Hubner, were released and collected at regular intervals across the cotton growing season, and the relationship between parasitism and different cotton cultivars determined. Egg and larval parasitism were significantly lower in the transgenic cottons than in the non-transgenic conventional cottons. The egg parasitoid recovered was Trichogramma confusum Viggiani and the predominant larval parasitoids were Campoletis chlorideae Uchida and Meteorus pulchriconis (Wesmael). Our studies indicate a potential negative interaction between transgenic cottons and parasitoids of CBW but need to be interpreted with caution because no within-year replication was used and treatments were not spatially randomised across years. none