Myocarditis is a well-recognized component of Kawasaki disease, with left ventricular dysfunction occurring in more than half of patients during the acute phase. The purpose of this study was to evaluate myocardial function in patients with Kawasaki disease using pulsed tissue Doppler imaging (TDI). Twenty-five patients with the diagnosis of acute Kawasaki disease were enrolled in the study. All patients underwent echocardiographic studies at the time of diagnosis of the disease, in its acute phase, prior to treatment, and then 4 weeks later. For an aged-matched control group with fever and no cardiac disease, the same echocardiographic evaluations were performed. Peak velocities of systolic (Sa), early diastolic (Ea), and late diastolic (Aa) motion of the annulus were obtained at the lateral and septal sides in apical four-chamber view, and TDI-derived myocardial performance index (TDI-MPI) was also calculated. Peak Ea velocity of lateral mitral annulus was decreased significantly during the acute phase of illness (14 +/- 4.40 vs. 17.67 +/- 4.41; P = 0.028). In seven patients with carditis, changes in Ea-to-Aa ratio of septum (1.28 +/- 0.278 vs. 1.78 +/- 0.49; P = 0.018) and lateral mitral annulus (1.23 +/- 0.496 vs. 2.11 +/- 0.822; P = 0.014) were statistically significant but TDI-MPI showed no statistically significant changes. This study showed that peak mitral annular Ea velocities obtained by TDI were significantly altered in the acute phase of Kawasaki disease. TDI- MPI does not add an incremental benefit to other indexes of myocardial performance for comprehensive myocardial function in the acute phase of Kawasaki disease.