A procedure with four chromatography steps was developed for the purification of DNA polymerase from Bacillus caldotenax by using fast protein liquid chromatography. The procedure was suitable for use with process-scale media. Elution profiles obtained from ion-exchange chromatography and triazine-dye affinity chromatography with fast protein liquid chromatography and process-scale media were similar. The enzyme showed stronger interaction, however, with phenyl-Sepharose FF in the scaled-up process than with the phenyl-Superose used in fast protein liquid chromatography. The surprising binding of the DNA polymerase to sulphonated ion-exchange media at pH 7.5 may be explained by the structure of the enzyme.