We report a case of a 73-year-old Japanese male patient who developed Behçet's disease (BD) after poststreptococcal acute glomerulonephritis. Three months after the initial presentation, acneiform eruption and oral and genital ulcers appeared. Treatment with oral prednisolone (20 mg/day) resulted in the remarkable disappearance of these symptoms. These findings support the hypothesis that Streptococcus pyogenes may be an etiologic factor of BD.