The objectives were to provide a reliable method for quantifying the Cry1Ac produced by transgenic cotton plants and to use this to examine the changes in Cry1Ac levels during a field season. We also undertook to train relevant laboratory personnel in Canberra and Narrabri in the use of the techniques for extracting and measuring Cry1Ac levels in plants. The project has been successful in developing a method for estimating the content of Cry1Ac in cotton tissues of all ages and developmental stages. Statistical analysis of the efficiency of extraction