Purpose: Intussusceptions are one of the most common causes of intestinal obstruction in infants and young children. Although it is easily treated by non-operative reduction using barium, water or air, this treatment is very stressful for young patients and may cause bowel perforation, peritonitis and shock. In this study, we identified the risk factors associated with the failure of non-operative reduction, to identify a group of children that would benefit from the procedure and those who would not. Methods: We reviewed the medical records of patients with intussusception who were treated at the Korea University Medical Center Ansan hospital from March 1998 to July 2006. Three hundred fourteen children with intussusception were identified. Among them, non-operative reductions were performed in three hundred. Clinical and radiological variables were compared according to the failure or success of the non-operative reduction. Results: Non-operative reductions were successful in 243 (81%) and failed in 57 (19%). The group that had failed procedures had a younger age (12.3${\pm}$17.2 months vs. 18.0${\pm}$15.8 months, p=0.03), longer symptom duration before reduction (33.6${\pm}$29.0 hr vs. 21.5${\pm}$20.3 hr, p<0.01), more vomiting and lethargy (p<0.01), but less abdominal pain and irritability (p<0.01), compared with the group that had a successful procedure. Logistic regression analysis showed that the factors associated with the failure of non-operative reductions were a younger age, less than 6 months of age (odds ratio: 2.5, 95% confidence interval: 1.2~5.2, p=0.01), duration of symptoms, longer than 24 hrs before reduction (odds ratio: 2.1, 95% confidence interval: 1.2~4.2, p=0.03), bloody stool (odds ratio: 4.8, 95% confidence interval: 1.9~12.2, p<0.01), lethargy (odds ratio: 3.4, 95% confidence interval: 1.1~10.4, p=0.04), and abdominal pain or irritability (odds ratio: 0.2, 95% confidence interval: 0.1~0.4, p<0.01). Conclusion: For children with intussusception, an age younger than 6 months, and duration of symptoms more than 24 hrs before reduction, as well as the presence of bloody stools, lethargy and abdominal pain or irritability were variables associated with failure of a non-operative reduction. Knowledge of these variables should be considered in making clinical decisions for therapeutic interventions.