Recently, changes in the serum CRP level 1/10 the concentration range ordinarily used as a marker of acute inflammation has received attention in relation to cardiovascular injury at the AACC/CDC joint forum at Atlanta held on March 13, 2001. We have succeeded in the development of recombinant human CRP(rCRP) by inserting the cloned CRP gene into expression vector pTRP, followed by transformation of E. coli. Genes encoding the signal peptide of E. coli alkaline phosphatase and kil gene were additionally inserted, so that rCRP can be secreted into the culture supernatant. Five grams of rCRP was purified from 180 L culture supernatant by affinity chromatography. The purified rCRP was indistinguishable from native rCRP with respect to Ca(2+)-dependent binding activity to phosphorylcholine, electrophoretic behavior in the presence or absence of SDS, N-terminal amino acid, and immunochemical properties. rCRP was found to have a potential as a reference material and/or calibrator for hsCRP assay.