The present status of the undeveloped branch of high-performance immobilized-metal-ion affinity chromatography (HPIMAC) is reviewed. As demonstrated, high resolution of peptides and protein mixtures can be obtained. Under specified conditions, more than 1000 runs can be made repeatedly on a single column without much change in pattern or recovery. Occasionally, 10(3)- to 10(4)-fold purification of a protein can be obtained in a single chromatographic run.