The distribution of the components of complement has been studied by the extracting method after filter-paper electrophoresis of guinea-pig serum. Then the following results have been obtained: 1) Mid-piece (C'1) is inactivated by filter-paper electrophoresis in 3 hours, 0.3 mA/cm. So the distribution of mid-piece is not able to make clear. 2) End-piece (C'2) is contained in α-globulin fraction of guinea-pig serum. 3) The third component (C'3) distributes mainly in β-, γ-globulin, and a portion in α-globulin. 4) The fourth component (C'4) is contained mainly in α-globulin, and a portion in β-globulin.