In Australia the two-spotted spider mite, Tetranychus urticae Koch, is regarded as a major pest of cotton. However, neither the pest status nor the ecology of spider mattes on cotton has been studied. Consequently management strategies are based on information derived elsewhere, which may not be relevant in Australia. Therefore the pest status of mites, their patterns of distribution and abundance on cotton and associated host plants, and the factors that influence these patterns were investigated. This project produced a large amount of information from a wide range of experiments. Rather than detail experimental methods, presentation is restricted to the key findings and their implications for mite ecology and management.