Thrips are important pests in Australian cotton and are also key predators of spider mites. Despite their pest status thrips have received little attention, with little known of their species composition, ecology, or their effect on cotton maturity or yield. The aim of the experiments described below is to investigate the effect of early season thrips infestations on the development, maturity and yield of cotton in order (1) to derive thresholds for thrips control, (2) to develop appropriate sampling recommendations and (3) to obtain infonnation to enable the effect of thrips to be linked with the Oz.cot and Cercot cotton crop models.