A method for total As and Cr determination in seawater sam- ples has been developed. As and Cr were measured using the seaFAST2 automated sample introduction system coupled to an ICP-MS. The sampling system allows on-line sample dilution (10 times) before introduction into the ICP-MS. Calibration was performed using the standard addition method, working in the concen- tration range of 0 to 50 μg L-1 for As and 0 to 25 μg L-1 for Cr. The method shows good sensitivity resulting in LODs and LOQs of 0.3 and 0.9 μg L-1, respectively, for As and of 0.03 and 0.09, respectively, for Cr determina- tion. The method was precise (RSD <2%) and accurate. This method was applied to the determination of As and Cr in different seawater samples from the Galician coast of Spain. The concentrations found ranged from 0.3 to 3.1 μg L-1 for As and from 0.03 to 0.1 μg L-1 for Cr.