To measure the activities of classical or alternative complement pathway using the modified Boyden's chemotactic chamber (each compartment 2ml and filter, pore size 3μ), suitable conditions were examined and the following results were obtained. 1) The upper compartment of the chamber contained 4×10(6) polymorphonuclear cells and 10% heat inactivated human serum in medium TC-199. 2) The lower compartment contained 10% fresh human serum as a complement source in medium TC-199. 3) To generate the classical complement pathway-derived chemotactic factor(s), 0.84mg of heat aggregated human Fr.Ⅱ was added to the lower compartment (4.2mg/ml fresh serum). 4) To generate the alternative complement pathway-derived chemotactic factor(s), 0.2mg of zymosan was added to it (1mg/fresh serum). 5) In this assay, the chemotactic activities derived from classical or alternative complement pathway were dose-dependent upon the serum (complement) concentrations in the lower compartment.