Background and Aims: Kawasaki disease (KD) is the leading cause of acquired pediatric cardiac disease and requires a timely diagnosis. Available effective therapy is ideally administered within 10 days of illness diagnosis. Recent reports of several laboratory tests in KD have been published. In this study, we aimed to evaluate the sensitivity and specificity of several laboratory tests. Methods: We performed a retrospective study of consecutive patients diagnosed with KD from January to December 2008. We studied the sensitivity and specificity of several different tests [T-cell subgroups, platelet count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP)] to predict KD using receiveroperator characteristic curve analysis. Results: No significant difference was demonstrated in T-cell subgroups between patients with KD and referent patients (P>0.05). However, platelet count, ESR, and CRP were significantly higher in patients with KD than in referent patients (P<0.05). ESR showed a sensitivity of 93.9% and specificity of 83.3% with a cut-off of 15 mm/hr (area under the curve [AUC], 89.1%; P=0.03). Platelet count showed a sensitivity of 70.6% and specificity of 75% with a cut-off of 336.5×109/l (AUC, 71.2%; P=0.03). Conclusions: These results indicate that platelet count and ESR are good predictors of KD. J. Clin. Lab. Anal. 24:385–388, 2010. © 2010 Wiley-Liss, Inc.