Here, we show a fast and sensitive method for the determination of inorganic arsenic in natural waters using differential pulse cathodic stripping voltammetry. All the arsenite determinations were done in 2.0 mol L-1 HCl + 3.15 x 10(-4) mol L-1 Cu(II) supporting electrolyte. 1 x 10(-3) mol L-1 sodium thiosulphate was used as As(V) reducing agent. The detection limit was 0.5 mu g L-1 for both species. The method has been applied to water samples collected in an arsenic-contaminated region of Brazil, in particular, to verify the efficiency of the solar oxidation and removal of arsenic process applied to these waters.53137141