PURPOSE: Acute appendicitis is very rare in infancy and early childhood. Delayed diagnosis of appendicitis may result in catastrophic outcome with perforation. We performed a retrospective analysis of clinical and radiologic findings of acute appendicitis occurring in the first 2 years of life. MATERIAL AND METHODS: Nine patients of acute appendicitis who were are less than two years of age proved by surgery and pathology were analyzed in terms of clinical symptoms and signs, and findings on preoperative plain abdominal roentgenography(9 cases), barium or gastrografin enema(6 cases), ultrasonography(8 cases) and abdominal CT scan(1 case). RESULTS: All patients presented with nonspecific clinical symptoms and signs, such as vomiting and fever. All were complicated with perforation. Six were associated with periappendiceal abscess, and four with appendicolith. Plain abdominal roentgenogram showed generalized paralytic ileus and increased density on right lower quadrant in all cases, and diffuse for right lower abdominal wall bulging in some cases. Most cases of perforated appendicities and periappendiceal abscess were diagnosed by ultrasound and some cases by contrast enema or abdominal CT scan. CONCLUSION: When the patients less than 2 years of age have nonspecific acute abdominal symptom with the roentgenographic findings of aggravating ileus and haziness in the right lower abdomen, ultrasonography might be considered as a helpful diagnostic tool for the early diagnosis of appendicitis. CT and contrast enema also might be helpful.