Cotton (Gossypium spp.) has been the first large-scale, agronomic crop treated with biological-control agents for suppression of seedling diseases and long-term chronic diseases of the rhizosphere. The vast majority of cotton seed planted in the United States is now treated with one or more biological-control agents (organisms). Standard chemical fungicides have two major weaknesses as seed treatments; they actively select for increased pathogen populations of organisms that are not controlled by their activity spectrum, and efficacy rapidly diminishes after planting. Biological-control agents are living organisms that control or suppress cotton rhizosphere pathogens. Generally accepted modes of action for biocontrol agents are antagonism (antibiosis), competition (niche exclusion), parasitism or predation, and induced systemic resistance (Deacon and Berry, 1993). Biological-control agents colonize the rhizosphere, and rhizosphere-competent strains maintain colonization until harvest. Biologicals supplement standard chemical fungicides through early synergy with chemicals. Biologicals also expand the activity spectrum, and they provide long-term activity. Use of biologicals in combination with chemical fungicides provides a classic example of integrated pest management, using the advantages of each component to provide optimum disease control. In order to be successful, biocontrol organisms must be dependable and efficacious, provide long-term storability under standard warehouse conditions, be compatible with chemical fungicides and insecticides applied to cotton seed, be compatible with current production practices, and provide demonstrated dollar returns to producers.