PURPOSE: The purpose of this study was to determine whether erythema at the BCG inoculation site in young infants is likely to be a diagnostic clue to Kawasaki disease (KD). METHODS: A retrospective study was performed in infants with KD aged < or = 3 months treated at our hospital from January 1998 to August 2003. RESULTS: Of 428 patients treated during the study period, 14(3.3%) were < or = 3 months of age. Of them, 13 had atypical presentations, with fewer classic findings in the required criteria of KD. The most common findings were fever(100%) and oral mucosal changes(78.5%). Erythema at the BCG inoculation site was observed in at least nine patients. This feature proved to be a definite evidence of the disease in three patients who had developed cardiac complications, and a strong diagnostic clue in the remaining six patients not having cardiac complications. Seven patients(50%) had developed cardiac complications:coronary dilatation in four patients, coronary wall irregularity in two, and mitral valve prolapse with regurgitation in one. During follow-up for 6 to 20 months, cardiac complications disappeared in all patients except for one who had mitral regurgitation. CONCLUSION: Most patients with KD < or = 3 months of age have atypical presentations, with a high rate of cardiac complications. Erythema at the site of BCG inoculation could be used as a reliable diagnostic tool for atypical KD in this young age group.