With the advent of new molecular genetic techniques, it is now possible to identify the particular pathogen strain in an outbreak of plant disease, to characterise it, and potentially, to isolate genes associated with pathogenicity. Similarly, such techniques can also be employed to differentiate between plant cultivars and progeny in plant breeding programs and in the identification of genes implicated in improved plant tolerance to diseases. The sensitivity of these techniques rests in their ability to detect the rare or subtle differences that exist between the genes of one individual and another. In the present investigation, we have applied Polymerase Chain Reaction (PCR). Random Amplified Polymorphic DNA {RAPD) -PCR and gene cloning techniques to strains of V. dahliae isolated from cotton plants. and to cotton cultivars tolerant to Verticillium wilt, with the aim of achieving a better understanding of this pathogenic disease in cotton.