The corrosion of brass in artificial seawater, (ASW), and in natural seawater, (NSW), collected at the beach of Ericeira, Portugal, was studied. The weight gains and the corresponding average corrosion rates of brass samples, immersed in both media, during periods of I week, 1, 3 and 6 months were determined. The concentrations of Cu2+ and Zn2+ ions in solution, produced by the corrosion of brass, were determined by atomic absorption spectrometry. The concentration of dissolved oxygen was also determined. The morphology of the corroded surfaces, with and without the corrosion products, was analyzed by visual observation and by scanning electron microscopy. The hydrated basic zinc chloro-sulfate compound, Zn-12(OH)(15)Cl-3(SO4)(3) (.) 5H(2)O, was identified by X-ray powder diffraction as the predominant compound in all the samples, particularly in those with longer exposure to NSW. It was concluded that the corrosion of brass in natural seawater is much higher than in artificial seawater.