Kawasaki disease (KD) is an acute multisystemic vasculitis occurring predominantly in children and rarely in adults. Diagnosis is made clinically using diagnostic guidelines; no specific test is available. "Incomplete" KD is a more recent concept, which refers to patients with fever lasting > or =5 days and 2 or 3 clinical criteria (rash, conjunctivitis, oral mucosal changes, changes of extremities, adenopathy), without reasonable explanation for the illness. To describe the clinical and laboratory features of classical (or "complete") KD, and incomplete KD in adults, we report 10 cases of adult KD, including 6 patients who fulfilled the criteria for incomplete KD, diagnosed either at presentation (n = 4) or retrospectively (n = 2). At the time of clinical presentation, complete KD was diagnosed in 4 patients, while 4 patients fulfilled the criteria for incomplete KD. For 3 of the 4 patients with incomplete KD, presence of severe inflammation, laboratory findings (hypoalbuminemia, anemia, elevation of alanine aminotransferase, thrombocytosis after 7 days, white blood cell count > or =15,000/mm, and urine > or =10 white blood cell/high power field), or echocardiogram findings were consistent with the diagnosis. In 2 patients, the diagnosis of KD was made retrospectively in the presence of myocardial infarction due to coronary aneurysms, after an undiagnosed medical history evocative of incomplete KD. Seven patients received intravenous immunoglobulins (IVIG), after a mean delay of 12.5 days, which appeared to shorten the course of the disease. This relatively large series of adult KD highlights the existence of incomplete KD in adults and suggests that the algorithm proposed by a multidisciplinary committee of experts to diagnose incomplete KD in children could be useful in adults. Further studies are needed to determinate whether prompt IVIG may avoid artery sequelae in adult patients with complete or incomplete KD.