Two days following a rat bite, a 3-month-old boy presented to the ED with a temperature of 40 C and several puncture wounds on his right hand. He died after a fulminating illness. Postmortem examination revealed endocarditis, interstitial pneumonia, hepatic and splenic congestion, and arthritis. Blood cultures revealed the presence of Streptobacillus moniliformis. Rat bite fever is rare in the United States, occurring most commonly in children and laboratory personnel.