To investigate the role of eosinophils in Kawasaki disease (KD) and the relationship to initial intravenous immunoglobulin (IVIG) treatment failure. A retrospective analysis of all children who were admitted and met the criteria of KD between 1999 and 2005. The patients were divided into IVIG-responsive and IVIG-resistant groups. A total of 185 patients were enrolled during the study period. A series of blood eosinophils and biochemistry studies were correlated to the effectiveness of IVIG. The neutrophils percentage before IVIG treatment (pre-IVIG), leukocyte counts within 3 days after IVIG treatment (post-IVIG), liver enzyme, albumin levels, and post-IVIG eosinophils percentage were all significantly different between the two groups in univariate analysis. Under multivariate analysis with logistic regression, post-IVIG eosinophilia [peripheral blood (PB) eosinophils >or=4%] had an inverse correlation to KD patients with IVIG-resistance (p = 0.003). Also, pre-IVIG hypoalbuminemia (albumin <or=3.0 g/dl) was positively correlated to IVIG-resistance (p = 0.018). Further analysis showed that the PB eosinophils was markedly increased in the acute stage and returned to normal 3 weeks after IVIG treatment (p < 0.001). Eosinophil levels are highly elevated in the acute stage of KD both before and after the IVIG treatment. Post-IVIG treatment eosinophilia has an inverse correlation to KD patients with IVIG-resistance and may indicate IVIG-responsive. This may be a valuable factor to survey for the necessity of a second dose IVIG treatment.