A study was made on the reactions of the cotton varieties commonly cultivated in the State of São Paulo (Brazil) to Verticillium wilt under field conditions. The effects of the disease were evaluated by determining the percentages of plants showing the symptoms of the Verticilliumwilt and by measuring the yield of each variety. The Fusarium resistant varieties IAC RM3 and IAC RM4 gave the highest yields and the lowest percentages of plants infected by Verticilliumwilt. It is suggested that these varieties might represent sources of resistance to Verticillium wilt.