The complexity and variability of both the biologicals and the bioassays used to test them led to the use of the reference standard- a sample of the product of defined purity and potency, against which all preparations of that product must be calibrated. In order to prepare and establish KFDA reference standard for recombinant human growth hormone (somatropin), somatropin substance was filled in ampoules in National Institute for Biological Standards and Control (NIBSC). The candidate KFDA reference standard for somatropin (designated as 98/674) was evaluated to determine the suitability of serving as a KFDA reference standard for somatropin by the collaborative study, in which 10 laboratories participated. Physicochemical analysis and in vivo bioassay were performed by direct comparison with the international somatropin standard 88/624. 98/674 was identified as somatropin by SDS-PAGE, IEF, peptide mapping, and HPLC. Determination of somatropin content by SE-HPLC yielded a mean estimate of 2.01 mg somatropin per ampoule. Data from the study also yielded mean values of 0.39 $pm$ 0.26% for high molecular weight impurities by SE-HPLC and mean values of 2.13 $pm$ 1.29% for somatropin related proteins by RP-HPLC. Estimates of relative potency by weight gain bioassay in the hypophysectomised rats showed that relative potency of KS 98/674 was 1.07 aganist IS 88/624. Based on the results of the collaborative study, the candidate reference standard for somatropin is suitable to serve as a KFDA reference standard for somatropin.