Dose-dependent, immune modulatory effects of aconitine and heated aconitine were studied in mice. Mice, administered aconitine and heated aconitine intraperitoneally every other day for 4 weeks, were sensitized and challenged with sheep red blood cells. Serum antibody titer, foot pad swelling and rosette forming cell number were measured to evaluate hurmoral and cell mediated immune responses. The results show that Humoral immune response was suppressed by aconitine 0.05 mg/kg and heated aconitine but increased by aconitine 0.10 mg/kg administration. Cell mediated immune response was suppressed in all groups. Especially heated aconitine administration significantly suppressed the cell mediated immune response. The number of peripheral circulating white blood cell was reduced by aconitine but was not affected by heated aconitine.