The behavior of three São Paulo cotton varieties (IAC 12, IAC 13 and IAC RM3), which differ themselves in vegetative cycle and nutrient requirements, after receiving three levels of complete N, P and K fertilization, were compared under cultivation on latossolic B "Terra Roxa" soils. The inclusion of the variety IAC RM3, resistant to Fusarium wilt, was made considering a possible spreading of this disease, now common in sandy soils, to clay soils. A basic dose of NPK fertilizer, containing 20, 45 and 40 kg/ha of N, P2O5 and K..O respectively, induced a significant increase in cotton yield, in relation to control plots, where no fertilizer was added. Among the varieties, IAC 13, with longest life cycle, presented the highest yield, followed by IAC 12, with intermediate cycle length. IAC RM3 was the less productive. There was also a significant increase in the weight of seeds and bolls due to this basic dose. No appreciable effect of a possible interaction between varieties and fertilization could be noticed. A double dose of fertilizer produced further increase in yield, except in the case of IAC RM3, in which additional amount of fertilizer induced a slight yield reduction and many plants showed signs of potassium defficiency. Considering the fiber characteristics the tested varieties differed significantly. IAC 12 had the highest mean of lint percentage, while IAC 13, on the average, was the best for Micronaire and Pressley indices, confirming previous unpublished determinations.