The Ca(2+)-standardization of Japan only may cause problems for the importation of foreign analyzers.

A serum based reference material for Ca2+ measurement has been established in Japan. cCa2+ in the reference material was assigned with a IFCC reference cell. Some improvements of the IFCC reference cell are described. A few non-Japanese Ca2+ analyzers have given very inaccurate results with the reference material. The Japanese authorities can therefore be expected to hamper their importation in the future. A world-wide external quality assessment scheme with the Japanese reference material is suggested to further identify and solve the problems.