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The aim of this study was to establish the first national standard for prekallikrein activator (PKA) calibrating to the first international standard PKA. A collaborative study among five laboratories, including three manufacturers and two national control laboratories, was carried out to evaluate the suitability of a candidate to serve as a national standard of PKA. The candidate was manufactured in GMP facility following approved human serum albumin fractionation procedure and freeze-dried 5% albumin solution containing PKA. Participants were provided with sufficient samples and asked to use lab-made prekallikrein substrate prepared in accordance with European Pharmacopeia and also to use a commercial prekallikrein provided as part of the study. The PKA concentration of the candidate was 61.8 IU per vial using lab-made prekallikrein. However, the concentration was 54.2 IU per vial using commercial prekallikrein. The variability obtained at each laboratory ranged from 1.9% to 5.1% for within-a-day and from 5.6% to 9.0% for day-to-day. The candidate showed excellent stability from accelerated degradation study and real-time stability study. As a conclusion, the candidate preparation was suitable to serve as a Korean National Standard for PKA., (Copyright © 2011 The International Alliance for Biological Standardization. Published by Elsevier Ltd. All rights reserved.)