DNA of Phymatotrichum omnivorum was examined from 21 cultures obtained from cotton and various other dicotyledonous plants from all over the state of Texas. The restriction enzyme fragment patterns of DNA were compared among the isolates for similarities and dissimilarities. Restriction fragment length polymorphisms were detected; but could not be associated to other traits such as sclerotial production, vegetative growth or disease progression. These studies definitely show diversity among the isolates and were a step forward to a possible classification system of the fungus into distinct groups.