Experiments were conducted in several localities of the State of São Paulo to study the production of four sunflower varieties in the presence and absence of a NPK fertilizer. The seed yields decreased from the variety Uruguai to Riscada, Aguapeí and Preta. While Uruguai produced remarkably more than the other varieties, the differences among the latter were smaller. The overall yield increase due to NPK was small, but the responses changed appreciably according to the variety and the previous treatment of the soils used for the experiments. In the areas which received no fertilizer in the previous year, the experimental fertilizer increased substantially the yields, principally of the varieties Uruguai and Aguapeí. Riscada was less responsive to the pertilizer application.