The results of this survey of 100 smallholders in the Makhathini Flats, KwaZulu-Natal give cause for cautious optimism regarding the impacts of Bt cotton. Farmers who adopted Bt cotton benefited from the new technology, according to all the measures used. Average yield per hectare and per kilogram of seed was higher for adopters than for non-adopters. The increase in yields and the reduction in chemical application costs outweighed the higher seed cost, even in a poor production season due to unusually heavy rainfall. Bt adopters suffered far less of a fall in yields than those who did not adopt. As yields and gross margins are partial measures of efficiency, deterministic and stochastic efficiency frontiers were measured. Both methods confirm the farm accounting results, showing that Bt cotton adopters were more efficient. For 1998, the results showed that adopters averaged 88% efficiency, as compared with 66% for non-adopters. In 1999, the equivalent figures were 74% and 48%. Similarly, the determinist frontier results for both years show that adopters were over 62% efficient, while non-adopters averaged only 46%.