Dietary manipulation can substantially lower ammonia (NH3) emissions from laying-hen houses or manure storage. Recent lab studies showed a NH3 emission reduction of 40– 60% for an experimental (EcoCal ^TM ) diet as compared to the standard or control diet. The study reported here was a field verification test about the effects of EcoCal diet on NH3, hydrogen sulfide (H2S) and carbon dioxide (CO2) emissions, hen production performance, and the economic returns for a commercial high-rise layer operation in Iowa. Comparative data were collected during December 2006 to May 2007. The results showed that the EcoCal diet led to NH3 emission reduction by up to 23.2% (0.86±0.04 vs. 1.12±0.03 g NH3 d ^-1 hen ^-1 for EcoCal vs. Control diet, respectively) while H2S emission increased by up to 134% (4.38±0.20 vs. 1.82±0.07 mg d -1 hen -1 for EcoCal vs. Control, respectively). However, H2S emissions were small for both dietary regimens.