Dairy farms are thought to emit large amounts of ammonia and therefore contribute to nitrogen (N) fertilization of natural ecosystems and provide precursors for particulates that adversely affect visibility and human health. The 2003 NRC report “Air Emissions from Animal Agriculture” made an urgent call for processed-based research that assists producers and regulatory agencies in developing strategies that improve air quality. Laboratory and more operational-scale cow chamber studies evaluated how beddings impact ammonia emissions from dairy barns. Laboratory studies revealed that beddings able to absorb the most urine generally emitted more ammonia than low absorbent beddings. Four tie-stall chambers were used to determine ammonia emissions from 4 beddings: composted manure solids (MS), newspaper (NP), pine shavings (PS), and wheat straw (WS). The 4 beddings were assigned weekly to 4 chambers each containing 4 heifers (410-615 kg heifer-1) for 4 consecutive one-week periods (4 reps) using a 4x4 Latin-square design. Ammonia emissions (g h-1 heifer-1) were similar (2.32) and highest (P<0.05) from MS and NP than from PS and WS, which had similar emissions (1.86). Average daytime emissions (2.25) were 20% greater than nighttime emissions (P<0.05). As a percentage of feed N, emissions from RM (17.0%) were greater than (P<0.05) from WS (12.6%), and emissions from NP (16.3%) and PS (13.6%) were similar to each other, and also to MS and WS. Total N recoveries, or the sum of N contained in manure, ammonia, and body weight gain divided by the sum of N contained in bedding and feed ranged from 86 to 109% with no recovery differences among the 4 chambers.