This paper reports a series of data on salinity, current, nutrient and dissolved oxygen concentration observed in the Cananeia-Iguape region. The circulation of the system is dominated by tides entering from Barra de Cananéia and Barra de Icapara. Due to differences in the ebb and flood periods in Mar de Cananéia and Mar do Cubatão, residual flows of opposite directions were observed in the bottom layers of these channels. Observations from January 1982 in Mar de Cananéia showed nutrient concentrations generally higher at high tide than at low tide. The same behaviour was not observed in July 1981, when the concentrations were lower than in January. Differences in nutrient distributions in Mar de Cananeia and Bata de Trapande-Mar do Cubatao are apparently related to local influence of mixing processes, as well as to local biological and chemical processes.