Understand the dynamics that governs the physical attributes of the environment is indispensable in every planning work and environmental management. This understanding assumes larger importance in coastal areas face the speed of the action of agents that there act. This process materializes in the relief transformations along the time. For this work, the Long Island was defined, with 74 Km of coast line, as study area. Located in the coast south of the State of São Paulo, this barrier island was formed by marine sands, linked to events glacio-iso-eustatic, and is component of an important Coastal Complex, denominated "Complexo Estuarino-Lagunar de Iguape/Cananéia". For the study of the geomorphologic evolution of this Island, maps was made en three different sceneries - 1962, 1974 and 1991, being used for this of stereoscopes equals of aerial photographies in the scale 1:25,000. Later on the three maps were transposed for the scale 1:50.000, allowing a good visualization of the material. Thus, starting from the comparison and overlap of the same ones, it can be proven the great morphologic variation presented by the Ilha Comprida, associated to the processes of erosion and deposition. The main verification is the increment, in area, in its northeast extremity, caused by the contribution of sands. The erosive processes is linked to the progress of the coast line in detriment of the Iguape Island. In the interior margin of the Ilha Comprida the constant joining of "islands" and sandy banks have been the main geomorphologic modification found.