Cotton wilt incidence, caused by Fusarium oxysporum f vasinfectum (Atk.) Snyder & Hansen, was studied on different artificial soil-substrates in three consecutive experiments. The physical factors of the soil studied were percentage of sand and the size of sand particles. In the first experiment using IAC-12 a susceptible variety, the greatest wilt incidence ocurred in the treatments having the highest percentage of sand. In the second experiment using the same variety the highest wilt incidence ocurred in the treatments consisting of fine and medium sized sand particles, when compared with the treatment consisting of coarse sand particles. In the third experiment a wilt resistant variety, RM4, was used and there were no diferences in wilt incidence on the different substrates.