Abstract A simple and rapid method is proposed for the determination of copper, zinc and iron in whole blood. The injected sample is mineralized in the flow system on passage through a microwve oven and the metals are determined by atomic absorption spectrometry. Prior sample destruction or removal of organic material prior to injection is not necessary. The required volumes for each analysis are 90, 60 and 100 μl for copper, zinc and iron, respectively. The relative standard deviations were less than 3% in all cases. There was good agreement between the results obtained with the flow-injection method and those attained by conventional spectrophotometric measurements.