It is well known that convulsions may occur in clinical course of Kawasaki disease. However, the features of such seizures remain unclear. Recent reports have hypothesized that proinflammatory cytokines may contribute to the genesis of febrile convulsions (FC). In the acute phase of Kawasaki disease, proinflammatory cytokines are elevated in serum and CSF. If cytokines play a role in seizure phenomena in patients with Kawasaki disease, FC and seizures in Kawasaki disease might share some clinical features. To clarify the clinical features of convulsion in Kawasaki disease, we investigated 7 patients with Kawasaki disease with convulsions who were diagnosed and treated from November 2003 to November 2005. We found several features of the seizures, as well as the onset age, were diffrent among these clinical entities. The onset of Kawasaki disease was characteristically before six months of age in all patients. Seizure clustering was seen in 5 patients and partial seizures in 4. Prolonged unconsciousness after seizures was seen in one patient, syndrome of inappropriate secretion of ADH (SIADH) in one other. One patient had markedly elevated IL-6 in CSF. These observations led us to speculate that the convulsion of Kawasaki disease may be attributable to an encephalitis. The results of this study suggest that seizure pathophysiology differs between FC and Kawasaki disease.