A method for the determination of apolipoprotein A-I, the major protein compartment of HDL, in human serum is described. Rapid and easy serum sample preparation, well separated Apo A-I peaks in the human serum electropherogram and good linearity of the peak area vs. concentration plot, covering the range of the clinically relevant Apo A-I serum contents, suggest the introduction of this method routinely in clinical laboratories.