Through relief indices obtained from circular samples on a planialtimetric chart (1:35,000), the characterization was made of five soil units occurring in the Ribeira de Iguape Valley in the São Paulo State and the efficiency of the indices in the discrimination between these soils was also tested. The relief indices utilized in this study were mean declivity, maximum altimetric amplitude and mean length of the slopes. The five soils studied were: a) Alic Yellow Lato sol - LAa (Pariqüera unit); b) Alic Latosolic Red-Yellow Podzolic - PVLa-1 (Taquaruçu unit); c) Alic Latosolic Red-Yellow Podzolic - PVLa-2 (Arataca unit); d) Alic Red-Yellow Podzolic-PVa (Vapamirim unit); e) Alic Cambisol - Ca-2 (Canfilito unit). The relief indices made possible the characterization and discrimination of the studied soils, and the most efficient indices for differentiating the five soil units were maximum altimetric amplitude and mean declivity.