A 4-year-old Japanese girl developed a sore throat and high fever. Her tonsils were enlarged, red and covered with a thick white membrane. There was marked leukocytosis (26,600 leukocytes per mm) and elevated C-reactive protein levels (23.3 mg/dL). Rothia dentocariosa was recovered from the throat swab; many Gram-positive cocci were observed in the smear from the pseudomembrane covering the tonsil.