Abstract: The Verticillium wilt is a vascular disease of cotton. The degree of infectivity varies in its location, i.e. base, middle and top of the midvein. In general, the percentage of the infected vessels increases aeropetally. Vessels filled with gummy substances and tyloses are also common. Two types of mycelia invading the vessels are visible, namely, the large mycelia of yellow-brown and the fine mycelia of dark brown in color. The disease may be classified into four grades according to the appearance of the diseased leaves. The degree of infectivity does not correlate well with the number of vessels infected at the base of the midvein However, some correlation does exist with the total number of infected vessels and those with gummy substances and tyloses.