This work was carried out in field conditions to study the effects of phosphorus increasing levels on the yield, seed oil contents and macronutrient concentration, except S, in the seeds and hulls of castor bean, cv. 'Guarani'. Six rates of phosphorus (0-40-80-120-160-200 kg of P(2)0(5)/ha) were used in randomized blocks, with five replications, on the low fertility of a São Paulo State soil (LVa). The results showed that phosphorus increased numbers of fruit per raceme, decreased hull percent in the fruit and increased seed weight per raceme. In consequence, there was a mean increase of the seed yield of 100,21%. With regard to nutrient contents in the fruits, it was verified an increase of phosphorus contents and a tendency to reduce the nitrogen contents in the harvested seeds from the treatment with phosphorus fertilization. Phosphorus effects on oil contents of the seeds were not well noted. Therefore, this will be better studied later.