[en] A simple and rapid method was investigated for the determination of ppb levels of cadmium and copper in water, by a dual channel atomic absorption spectrophotometry with electrothermal atomization. The optimum operating conditions on the simultaneous determination were as follows: drying at ca. 180⁰C for 30 s, ashing at ca. 470⁰C for 60 s, atomization at ca. 2700⁰C for 10 s, and argon flow rate of 3 l/min. Sample solutions were acidified with nitric acid, because both cadmium and copper signals became maximal and constant over the range of 0.1 to 0.5 N in nitric acid and the addition of nitric acid was effective to decrease the non-specific absorption caused by sodium or potassium chloride. For sample volumes of 20 μl, the calibration graphs were linear up to 2.5 ppb for cadmium and up to 250 ppb for copper. The relative standard deviations of 2.4% and 1.4%, respectively, were obtained at the analytical levels of 2.0 ppb for cadmium and 200 ppb for copper. On the determination of cadmium, the permissible amounts of some diverse ions, such as K⁺ and Pb²⁺, increased greatly by making use of the peak-area instead of the peak-height as a measure of absorbance. This method was applied to the analysis of river and waste water, and the results were in good agreement with those obtained by the background correction method. (auth.)