Disease surveys in November and March of each season have been undertaken on a regular basis since 1983. The results of these surveys indicate the relative importance of those diseases which are present and provide an indication of the effects of various cultural and environmental factors on disease development. Disease surveys also present an ideal way to monitor the effects of disease control strategies as they are implemented. Verticillium wilt is the most widespread and important disease of cotton in Australia with the potential to reduce yields by 20-25% in some fields when weather conditions are favourable. Seedling disease is always present and effective control is important so that the costs and problems associated with replanting can be avoided. Mycorrhizas have been shown to be important in the early season growth of cotton in some areas. The purpose of these studies was to develop recommendations to growers for the more effective control of verticillium wilt and seedling diseases and to develop a better understanding of the importance of mycorrhizas so that cropping strategies to maximise early season growth of cotton seedlings can be developed. The increasing importance of Black root rot, the recent occurrence of Fusarium wilt and the significant epidemics of altemaria leaf spot in Pima cotton have also demanded attention.