The past growing season (1997/98) was the second commercial year of INGARD cotton varieties with some 60,000 ha planted across all growing regions. In the first two seasons of commercial use INGARD varieties have reduced pesticide use by 50-60% and achieved similar or better yields to conventional varieties. This represents a significant step forward in reducing pesticide use in the cotton industry. There have been several reports from CRDC and Monsanto regarding the performance of INGARD crops in relation to pesticide use and economic value to growers and I don't intend covering these issues here. Obviously the bottom line when it comes to INGARD performance is efficacy, an issue which is amenable to research. To provide most value and ease of management, transgenic cotton crops need to provide consistent and hopefully high capacity to kill the target pests quickly ie. high efficacy. Early in development of transgenic cottons the expectation was that expression of the Bt protein would be consistent throughout growth of the crop and consequently that control of the target pests would be provided almost season long. The Cry1Ac gene is driven by a promoter which gives constitutive expression in all tissues in the plant, although there are significant differences between plant structures in the level of Bt protein production. However, from the very first year of small scale field trials it soon became evident that efficacy of leaves and reproductive tissues declined during plant growth and that some larvae were able to survive beyond first instar. It was not until lNGARD crops were grown on a commercial scale that the magnitude of these changes, and the variability which can occur between crops in different fields, farms and regions became fully apparent.