The measurement systems in clinical laboratory tests are being standardized, and variations in measurement values such as those of clinical chemistry tests among institutions have decreased. Though the compatibility of clinical tests' values is being established, reference intervals differ among institutions. Therefore, to clarify problems for the standardization of reference intervals, the Society of the Hitachi Automatic Clinical Analyzer sent out a questionnaire survey on problems regarding standardization in institutions. The questionnaire consisted of 40 items relating to blood examination, clinical chemistry tests, and immunological examination. 27 institutions responded. The results of the questionnaire showed that many institutions look favorably upon the standardization of reference intervals. However, they had a cautious attitude regarding the establishment of the reference intervals for items showing differences in reactivity among reagent kits or having no wide-spread measurement system. They appeared to consider that the standardization process is accompanied by many difficulties. Unless the nationwide standardization of reference intervals is achieved at the scientific society level, approval on the clinical side may be difficult to obtain. How to obtain clinical understanding is a problem. Nationwide data sharing has been advanced, and the standardization of reference intervals should also be advanced at the national level.