A microplate method for total hemolytic complement (CH 50) assay was described. The effect of unlysed sensitized red cells on the absorbance at 405mμ was minimal and the complement dependent hemolytic curve was similar to those obtained by Mayer's method. The mean titer of normal 19 sera showed 226±56 (mean±ISD) and the correlation coefficient to the titers obtained by Mayer's method in various disease sera was 0.92 (n=41).
