This research work was carried out, utilizing the castor bean cultivars 'IAC-38' and 'Campinas', in order to evaluate the effects of increasing levels of nitrogen, phosphorus and potassium and interaction of the levels of these three nutrients on yield. For this purpose, two experiments were conducted in 1968/69 and 1969/70, in a yellow dark latossol, sandy phase, located in São Manuel, State of São Paulo. These experiments were a 3 x 3 x 3 factorial design. The following levels were used: 30, 60 and 120 kg/ha of nitrogen; 40, 80 and 160 kg/ha of P2O5 and 20, 40 and 80 kg/ha of K2O. Nitrogen and potassium did not increase yield when applied alone, but phosphorus showed positive effects when applied with potassium or alone. Eighty kg/ha of P2O5 yielded 22,56% and 111,51% more beans than 40 kg/ha for cultivars IAC-38 and «Campinas», respectively. On the presence of 40 and 80 kg/ha of K2O, the yields with P2 and P3 were higher than that with P1. The results show also that phosphorus increased bean density.