In recent years, structural changes in the hog sector, including increased farm size and regional shifts in production, have altered manure management practices. Also, changes to the Clean Water Act, State regulations, and increasing local confl icts over air quality issues, including odor, have infl uenced manure management decisions. This study uses data from two national surveys of hog farmers to examine how hog manure management practices vary with the scale of production and how these practices evolved between 1998 and 2004. Included are the effects of structural changes, recent policies on manure management technologies and practices, the use of nutrient management plans, and manure application rates. The fi ndings suggest that larger hog operations are altering their manure management decisions in response to binding nutrient application constraints, and that environmental policy is contributing to the adoption of conservation compatible manure management practices.