Prior to the 1992-1993 cotton season, Australia was considered to be free from the fungal disease of cotton known as Fusarium wilt. The disease is caused by a soil-inhabiting fungus, Fusarium oxysporum f.sp vasinfectum (Fov), and two different strains of the causal pathogen have since been described in Australia (Kochman, 1995; Davis et al 1996; Kochman, et al 1998; Bentley et al these proceedings). These strains, described as Vegetative Compatibility Groups (VCGs) 01/11 and 01/12, have caused severe losses to cotton production in Australia, particularly in susceptible varieties. Fov is now considered by many growers, ginners, consultants and other industry personnel as the most important constraint to sustainable cotton production in Australia to have developed in recent years