The incidence and severity of Fusarium wilt of cotton is increasing in the San Joaquin Valley. In 1967 its incidence was confined to two or three fields and probably less than 100 acres; in 1982, however, Fusarium wilt was known to be prevalent in over 50 fields and affecting greater than five thousand acres of cotton land. Since the disease involves the interaction of Fusarium oxysporum f. sp. vasinfectum (FOV) and Meloidogyne incognita (MI), methods for disease control extend to the management of either or both of these soil-borne pathogens. The objectives of the present research were to define the effects of soil inoculum densities of FOV and MI on earliness, rate of development, and incidence of Fusarium wilt in relation to cotton plant phenology and lint yields.