The capacity of tobacco infusions of Korean cigarettes to activate the complement pathway was investigated in vitro by hemolytic assay. Complement activity was studied using samples of normal rabbit serum incubated at $37^{circ}C$ with tobacco infusions. In all mixtures containing tobacco infusion A, B, C, D, E, F, G, H and I at a concentration of 0.1 : 1, total hemolytic complement showed a progressive decrease of 55.92%, 48.62%, 42.89%, 49.12%, 42.26%, 52.26%, 71.96%, 60.90%, and 61.14% respectively, after 60min of incubation. This study suggests that all tobacco infusions of Korean cigarettes are activators of complement.