Mesenteric cysts are rare intraabdominal lesions of childhood that may vary in presentation from an asymptomatic mass to an acute abdomen. From 1970 to 1990, 15 children were diagnosed and treated for mesenteric cysts at Ste Justine Hospital in Montreal. The ages ranged from birth to 18 years (average age, 6 years). There were 9 boys and 6 girls. Ten patients required emergency surgery and five underwent elective surgery. The main presenting symptom was abdominal pain. Ten patients had preoperative ultrasounds that were diagnostic for a cystic mass in all patients. The second most frequent preoperative diagnosis was appendicitis. The cysts were located in the small bowel mesentery in 5 cases, the base of the mesentery with retroperitoneal extension in 4 cases, the transverse mesocolon in 4 cases, and the gastrocolic ligament in 2 cases. Operative procedures performed included complete cyst excision (9 patients), complete excision with intestinal resection (5 patients), and drainage of the cyst (1 patient). The only recurrence in this series occurred after drainage. One other patient had recurrence of a mesenteric cyst following resection performed elsewhere. Mesenteric cysts are rare in children, are usually symptomatic, and are most commonly misdiagnosed as acute appendicitis. Accurate preoperative diagnosis is possible with current ultrasonographic imaging techniques. Complete cyst resection is the procedure of choice and results in an excellent outcome.