The studies on the root system of the bean plant (Phaseolus vulgaris L.) developed in two types of soils of the State of São Paulo were carried out to serve as a basis for a better understanding of the problems connected with the application of mineral fertilizers to this crop. The results obtained showed that a great percentage of the roots (74.5% in Massape soil and 87.4% in the Arenito de Bauru soil) is found in the upper 10cm soil layer and practically all in the upper 20cm of soil (83.6% and 97.4%, respectively).