Individual plant selection, followed by progeny tests, in naturally infested soil located in cotton growing areas of the State of São Paulo, revealed to be a viable method to improve cotton varieties, resistant to Fusarium wilt. IAC RM4 variety, obtained by this method, was superior to the paternal variety, Auburn 56, in fiber and agronomic characteristics, besides resistance to Fusarium wilt. The effectivenness of this method is discussed on the basis of the great number of plants that is possible to be selected, a factor which is limitant in the case of artificial inoculation.