Yersinia enterocolitica enteritis is a potentially treatable infection. To understand its seasonal incidence and clinical presentation in children, we reviewed case records of children seen in Cardinal Glennon Children's Hospital in St. Louis, MO. We found the incidence of Yersinia enteritis to be as frequent as enteritis caused by Campylobacter. It occurred more frequently during the winter months (P < 0.002) than during the rest of the year. Fever was common in infants with Yersinia enteritis. Abdominal pain and distention were infrequent. Seventeen (35%) patients were 3 months of age or younger; 4 of 17 (28%) developed Yersinia sepsis as a complication of the enteritis. Physicians should perform stool cultures for Y. enterocolitica in young infants who present with high fever and diarrhea in winter months, especially when there is blood in stools or the patient appears septic.