The US has higher infant mortality than peer countries. In this paper, we combine micro-data from the US with similar data from four European countries to investigate this US infant mortality disadvantage. The US disadvantage persists after adjusting for potential di erential reporting of births near the threshold of viability. While the importance of birth weight varies across comparison countries, relative to all comparison countries the US has similar neonatal (<1 month) mortality but higher postneonatal (1-12 months) mortality. We document similar patterns across Census divisions within the US. The postneonatal mortality disadvantage is driven by poor birth outcomes among lower socioeconomic status individuals.