The repetitive analysis of serum lactate dehydrogenase (LDH) isoenzymes has been performed on a weak anion exchanger (TSKgel DEAE-5PW), which was developed by introducing diethylaminoethyl groups into TSKgel G5000PW (10 microns particle diameter)--a hydrophilic polymer-based material of large pore size--for high-performance gel chromatography. By use of this anion exchanger, a high-pH (greater than 8.0) solvent could be used and the albumin peak was completely separate from the LDH isoenzyme peaks. After 10 successive analyses with an autosampler, the coefficient of variation of the LDH isoenzyme elution times was less than or equal to 0.90%, and the coefficient of variation for peak areas was less than or equal to 3.85%. After 40 successive analyses, resolution between isoenzymes was generally greater than 1.25. This column can be used for more than 300 intermittent injections of human serum.