The measurement of total serum hemolytic complement activity is a useful screening test for the integrity of the complete complement system of the classical pathway and hemolytic titration (CH50) assay is most commonly used. The purpose of this study was to examine serum values for total hemolytic complement (CH50) activity by the method of Mayor in 100 normal Korean adults in the age range from 18 through 57 years. The values showed Gaussian distribution, and we obtained reference range of 18-35 CH50 units/ml with tolence limits set for 95% of the general population.