OBJECTIVE: We attempted to obtain baseline data on the incidence of intussusception and its association with gastroenteritis in a cross-sectional observational study in children. METHODS: Admissions to all 38 pediatric units in Switzerland because of intussusception were reported to the Swiss Pediatric Surveillance Unit from April 2003 to March 2006. Patient and disease characteristics were assessed prospectively with the use of a standardized questionnaire based on the case definition for intussusception developed by the Brighton Collaboration. Completeness of reporting was verified through capture-recapture analysis. RESULTS: There were 294 patients with reported intussusception; 35 cases were excluded for various reasons, and 29 additional patients were identified through International Classification of Diseases, 10th Revision, codes. After capture-recapture analysis, we estimated underreporting to the Swiss Pediatric Surveillance Unit to be 32% and we calculated a true number of 381 intussusception episodes. The highest level of diagnostic certainty was reached by 248 patients, and 20 fulfilled level 2 criteria; for the remaining 20 patients, available information was insufficient. The mean age of the patients was 2.7 years. The yearly mean incidence of intussusception was 38, 31, and 26 cases per 100,000 live births in the first, second, and third year of life, respectively, with no apparent seasonality. Seventy patients had a history of coinciding gastroenteritis, and 5 of 61 tested positive for rotavirus. Spontaneous devagination was observed for 38 patients; enemas reduced intussusception successfully in 183 cases, whereas surgical treatment was required in 67. All patients recovered without sequelae. CONCLUSIONS: This is the first prospective nationwide surveillance of intussusception in childhood using a standardized case definition. Most cases occurred beyond infancy, and association with rotavirus gastroenteritis was rare.