With the aim to verify as phosphorus can increase castor bean yield, an experiment was conducted, using the "Campinas" cultivar. It was laid out during season of 1971-1972 and the experimental design was in randomized brodkss, with five replications and six rates of phosphorus, 0 - 40 - 80 - 120 - 160 - 200 kg of P2O5/ha. According to the data, the following conclusions can be drawn. There was an increase of the seed production of 320% when the data of the treatments with prosphorus were compared with that without phosphorus. This is due to the fact that phosphorus increased the number of fruits by raceme and by plot, the seed weight, and decreased the percentage of hulls in the fruits. Among the racemes, the first one gave better response to phosphorus. Fertilizer phosphorus application increased the phosphorus content of the seed and showed a tendency to diminish the nitrogen content of the hulls. The oil seed content was not affected by the phosphorus addition in soil.