Verticillium dahliae was frequently isolated from cotton plants showing severe leaf symptoms of potassium deficiency (K-def). Among the isolates recovered, approximately 23% produced white colonies on potato dextrose agar medium whereas the other isolates produced grey (25%) or black microsclerotial colonies (52%). Field-grown cotton plants were injected with sterile water or stem-inoculated with conidia from four white isolates or one black microsclerotial isolate. Plants inoculated with the isolates of V. dahlias developed leaf symptoms similar to plants with K-def; in some plants, symptoms typical of Verticillium wilt also developed. The isolates were recovered from inoculated plants whereas no isolates of V. dahliae were obtained from the healthy water-injected plants.