South Africa is one of few developing countries, and the only one in Africa that has adopted genetically modified crops for commercial producton. The very impressive adoption rate of insect-resistant cotton in South Africa can be attributed to different benefits enjoyed by adopters. This article focuses on the reasons and effects of Bt cotton adoption by large-scale and small-scale cotton farmers in South Africa and considers the impact of the adoption on yields, cost and profit. In addition the paper also analyses the production efficiency of adopters and non-adopters. Boh large-scale and small-scale farmers enjoy financial benefits due to higher yields and despite higher seed costs. In addition, those who adopted the technology appear to be more technically efficient than those who do not adopt – indicating that it is perhaps the better farmers who spot the potential benefits of the Bt cotton seed. Furher diverse analysis of the results from the varous surveys are underway and promises to deliver interesting results on the various impactsBt cotton is having on the South African cotton industry.