11 cases of Kawasaki's disease were studied: the patients originated from Toscana and had at least 5 to 6 of the major criteria established by the Japanese Committee for Research to diagnose Kawasaki's disease. No toxic or infectious agents could be identified. We believe, like many other authors, that the responsible agent must be searched for in the patient's environment. Genetic predisposition also plays an important role, as demonstrated in the Japanese population. Our study of 9 patients yielded no conclusive results concerning the role of genetic factors. Only a study involving a much greater number of patients could establish whether genetics plays a major role in the development of the disease.