The view that the US economy and living standards benefited from mobilization for World War II is commonplace. The main source of evidence is aggregate comparisons of standard macroeconomic variables over the Great Depression and war years. In this paper, we use newly collected data on infant health and industrial accidents to document changes in health conditions during World War II. The findings suggest that infant health and work conditions deteriorated in the early 1940s. Opening or expanding a plant for war production is associated with 7 additional infant deaths (per 1,000 live births) in 1942 and incidence of industrial accidents increased by 16 percent. The war years interrupted the long-run trend toward improved health along a number of dimensions, however, recovery to pre-war levels occurred quickly after 1945.