Background Although Kawasaki disease (KD) is known to cause anemia,the relationship between its prognosis and hemo?globin level is less well known.Methods We herein performed a secondary analysis of data from a previous study (Post-RAISE).Children aged 6 months to 2 years at the time of KD diagnosis were enrolled.Decreased hemoglobin was defined as a decrease＞ 10％ on post-treatment day 2 compared with the level prior to the initial therapy.Results Of 1253 KD cases,treatment resistance was observed in 209 (17％) and was significantly more frequent in the decreased hemoglobin group (37/167 vs.172/1086,P=0.041).Multivariable logistic regression analysis revealed that decreased hemo-globin was associated with resistance to the initial treatment (odds ratio 1.53;95％ confidence interval 1.00-2.33;P=0.048).Conclusions Decreased hemoglobin was significantly associated with resistance to initial treatment in patients with KD.