The operative experience with 333 children (179 [54%] under one year of age) is reported. Associated cardiac anomalies were present in 75%. All those requiring operation before the age of one year had congestive heart failure. Early recognition of the failure of medical treatment and early operative correction are imperative if an avoidable fatal outcome is to be prevented. This study demonstrates that the operative mortality is small (2.8%) in patients over the age of six months, and that almost half of the very ill infants under six months of age can be saved by early operation.