OBJECTIVES: Over the last two decades, catheter ablation (CA) has revolutionized the treatment of pediatric tachycardia by providing a relatively safe alternative to open-heart surgery or lifelong pharmacotherapy. Despite its high success rate, however, CA has some risk of major complications, such as complete or second-degree atrioventricular block, and a higher risk of minor complications, such as hematoma.  No study to date has estimated national frequencies and costs for CA and its complications in children. The objectives were to 1) determine the frequency of CA; 2) determine the extent of major and minor complications associated with CA; 3) estimate the average cost and length of stay (LOS) for children undergoing CA; and 4) predict the likelihood of major complications based on patient and hospital characteristics. METHODS: Data were obtained from the Kids’ Inpatient Database (KID) for the years 2000, 2003, and 2006.  Discharges were selected if CA (ICD-9 code 37.34) was listed as a primary or secondary procedure.  Costs were computed using the KID cost-to-charge ratios. Logistic regression was used to predict the odds of major complications. RESULTS: In 2000, there were 1977 pediatric CAs; in 2003, there were 2049; and, in 2006, 2254. CAs involving children 0-11 months old increased 2.8 fold between 2000 and 2006. The percentage of visits involving CA complications ranged from 5.56% in 2000 to 7.72% in 2006.  In 2006, the mean cost and mean LOS for visits with CA were $19,425(±$1,022) and 2.39(±0.2) days, respectively. The odds of major complications from CA for atrial tachycardia were twice (p<0.01) that of supraventricular tachycardia. CONCLUSIONS:  In 2006, the national inpatient cost of CA and its complications totaled $43,783,950.  Since major complications are significantly more likely in young children (up to 6 years old), caution is required as more such procedures are performed in this age group.