Although neonatal intensive care has been praised widely for individual successes, its effectiveness has not been established systematically or conclusively. The literature consists principally of reports from individual intensive care units with sample sizes too small for statistical validation or generalization. This study analyzes the results obtained by recalculating and pooling the isolated reports. In addition, the findings of the solitary clinical trial, some scattered epidemiologic data, and several analyses of regional birthweight-specific time series data are reviewed. Taken together, this constitutes a body of evidence that supports the conclusion that intensive neonatal medical care has played a significant role in bringing about the impressive reduction in infant mortality that has taken place in this country since 1965.