Background: In Kawasaki disease (KD), myocardial inflammation has been shown to cause aberrations in cardiac function. Several recent studies have discussed the usefulness of tissue Doppler imaging (TDI) to evaluate left ventricular function. In this study, we used TDI to evaluate disturbance of myocardial function in the time-course of KD. Subjects: The KD patients group consisted of 59 children, aged 0.3-8.0 years. Age-matched control group consisted of 30 children. Methods: Echocardiographic examination was performed in the acute phase (before treatment for KD), the subacute phase (after treatment for KD), the convalescent phase and the late phase (3-14 months after KD onset). From the apical 4-chamber view, sample volume was placed at the lateral corner of the mitral annulus. The following measurements were obtained from the TDI recordings: peak systolic velocity (Sm), early (Em) and late diastolic velocities, isovolumic contraction time, ejection time, isovolumic relaxation time. Mitral inflow velocity (E)/Em and Tei index (TI) were also calculated. Results: (1) E/Em in the acute phase was significantly more increased than those in control and the other phase. (2) Sm in the subacute and convalescent phase were significantly more decreased than those in control and the late phase. (3) TI in the acute, subacute and convalescent phase were significantly more increased than those in control and the late phase. Conclusion: Latent abnormal tissue Doppler profiles, possibly reflecting systolic and diastolic dysfunction have been noted in KD patients. These findings suggest that TDI may be useful method for the detection of impaired myocardium in KD patients.