With the pending new CLIA regulations, the issue of standardization has become more important. AACC’s efforts in the areas of standardization and development of standard methods are well recognized and many members have participated in these efforts. As a result of a conference held in 1977, the National Reference System for the Clinical Laboratory (NRSCL) was established; responsibility for it was assigned to the National Committee for Clinical Laboratory Standards (NCCLS). The National Reference System has credentialed many analytes and their associated reference technologies since that time, much of this work having been performed by working groups of the AACC. Many of these efforts were joint efforts of AACC, NCCLS, National Institute of Standards and Technology (NIST; formerly National Bureau of Standards, NBS) and the NRSCL. One area of active interest for these groups has been the standardization of direct potentiometric measurements for sodium and potassium. The discrepancy of sodiumipotassium results between direct ion-selective electrodes (ISEs) and those methods that require predilution of the specimen (indirect ISE and flame photometry) is well documented (1, 2). It is also clear that sodium determinations by direct ISE systems from varions manufacturers do not currently give identical results for identical specimens (3). This is due both to differences in instrument design and calibration materials. In 1983, a Workshop on Direct Potentiometric Measurements in Blood was held in Gaithersburg, MD, under the cosponsorshipof NCCLS and the NBS (now NIST), to examine the factors that affect these measurements and to determine what decisions and data were necessary to establish standardization (4). The report by Gunaratna et al. in this issue is a result of these initial efforts. It demonstrates cooperation in the field among professionals from all disciplines because the reported studies were supported financially by eight instrument manufacturers who participated in the round-robin series, plus scientists from NIST and several hospital-based clinical chemists. It is this type of cooperative effort that characterizes the above-mentioned groups and has led to significant results in all areas of standardization. The overall objective of this study was the development of suitable reference materials, certified for concentrations of sodium and potassium, to be used in the standardization of direct ISEs. The efforts and materials reported in the paper provide a pragmatic solution to solve this problem and bring conformity to the field. It also allows laboratories to report results for Na/K by any of the methods in terms of the same reference range, and it ensures comparable results for specimens with normal protein and lipid concentrations. This solution was strongly supported by the Area Committee on Clinical Chemistry of NCCLS and its Subcommittee on Electrolytes (6). Given that these efforts had the support of instrument manufacturers, clinical chemists, and the NIST, the level of acceptance in the field is felt to be high. It is hoped and expected that a similar approach will lead to certified reference materials for many other analytes.