In order to obtain information of its environmental fate under conditions of use in the Australian cotton industry, this major study was initiated in 1990-91. It represented the first case of a systematic analysis of the fate of endosulfan under Australian conditions. The experimental strategy used was to conduct random sampling of soil throughout the year on several fields used for cotton growing. From analysis of these soil samples for endosulfan residues, it would be possible to discover the rate of breakdown and to estimate half-lives (the time to reduce the concentration in soil to half its current value) and to identify the chemical products. This would allow an assessment of whether endosulfan was likely to cause long-term problems related to its accumulation in soil and its potential threat to the environment.,