Purpose : The reticuloendothelial system is composed of sinusoidal capillaries, through which even large protein molecules are freely movable between plasma and interstitial space, including the lymphatic system. Therefore, high-dose intravenous immunoglobulin (IVIG) would cause a redistribution of proteins between two compartments. To investigate this hypothesis, we measured plasma protein and lipid levels in patients with Kawasaki disease before and after high-dose IVIG treatment. Methods : Thirty four children with Kawasaki disease who had complete responses to high-dose IVIG treatment (1 g/kg/day for two consecutive days), were analyzed. Before and after the administration of IVIG, serum analyses were performed for such parameters as total protein, albumin, ${\gamma}$-globulins (IgG, IgM, IgA), ${\alpha}1-$, ${\alpha}2-$, and ${\beta}-$ globulin fractions, and lipid profiles (total cholesterol, HDL-cholesterol, LDL-cholesterol and triglyceride). Results : The levels of ${\gamma}$-globulins including IgG, IgM, IgA were significantly increased, and IgG was increased by $1,779{\pm}304mg/dL$ after two-dose of IVIG infusion. The levels of albumin, ${\alpha}1-$, ${\alpha}2-$, and ${\beta}$ globulin fractions were significantly decreased by 18 percent, 24 percent, 19 percent and 12 percent, respectively. HDL-cholesterol level was significantly decreased by 20 percent, while LDL-cholesterol and triglyceride levels were significantly increased by 21 percent and 50 percent, respectively. The total cholesterol level was not changed. Conclusion : High-dose IVIG treatment decreased the levels of a variety of proteins except immunoglobulins, and the increase of IgG after IVIG treatment was lower than expected. Our results suggest that a part of infused IVIG and plasma proteins, including etiologic proteins for Kawasaki disease, may be distributed to the extravascular compartments. The rapid improvement of symptoms induced by IVIG in Kawasaki disease might be explained by this mode of action of IVIG.