A stopped flow method for the determination of dopamine and methyldopa is proposed. The method is based on the aerial oxidation of these catecholamines in strong alkali medium. The method was optimized using a spectrophotometer (λ = 360 nm) as detector. Calibration graphs were linear up to 2 × 10−4mol/L for dopamine and 3.0 × 10−4mol/L for methyldopa with quantification limits of 3.5 × 10−6mol/L and 4.3 × 10−7mol/L for dopamine and methyldopa, respectively. The method was successfully applied to the determination of catecholamines in pharmaceutical formulations.