Soil-borne strains of F. oxysporum are involved in the mechanisms of soil suppressiveness to Fusarium wilts, and many attempts have been made to use strains of Fusarium oxysporum to control Fusarium ...diseases. The modes of action of the protective strains are diverse; they include direct antagonism, competition for nutrients, and indirect antagonism through induced resistance of the plant. The use of newer tools has enabled a reconsideration of these modes of action; e.g., competition for infection sites whose importance has been minimized, and to make progress in the understanding of the interactions between the plant and either pathogenic or protective strains of F. oxysporum. Even though the mechanisms of biocontrol of F. oxysporum are far from being understood, several processes of mass production have been developed to enable field application of the biocontrol strains. These strains possess a strong ecological fitness and establish in soil of different physico-chemical properties. Their introduction into the soil does not durably modify the structure of the soil-borne communities of fungi and bacteria, indicating that their use does not present any risk to the environment.