The isopod species of rocky shores and shallow infralittoral zone from Enseada do Flamengo, Ubatuba, were studied. The sampling was done during Autumn (1965) and during Autumn and Springtime (1975) at six stations classified according to wave exposure. The intensity of the waves and the type of substratum showed to be important factors influencing distribution, abundance and diversity of the fauna. The highest density of isopods occurred in Dictyota ciliolata. A relation between species diversity and the degree of wave action was disclosed. Species diversity rised from exposed to moderately exposed sites and decreased with the increase in shelter.