Dietary manipulation can substantially lower ammonia emissions from laying hen manure. However, such dietary changes would be of little value if the changes cause inferior egg production and hen performance. Therefore, the objective of this study was to evaluate the effect of a diet containing EcoCalTM (gypsum and zeolite), which has been shown to lower ammonia emission in laboratory-scale testing, on hen production performance in commercial high-rise laying hen houses. A companion paper describes the effect of the EcoCal diet on ammonia, hydrogen sulfide, and carbon dioxide emissions. Two high-rise houses, each containing approximately 255,000 hens, were used for the study. Hens in one house were fed a diet containing 3.5% EcoCal, whereas hens in the other house were fed an EcoCal-free, control diet. The cooperating farm provided the production records. The comparative production data have been collected since October 2006 and the study is scheduled to continue for another 2 years (i.e., through 2009). The period was broken into 2-wk increments for data analyses. Feed consumption was higher for the EcoCal-fed hens from 100 to 105 weeks of age. Egg production was transiently lower for the EcoCal-fed hens during the 92 to 93 wk-of-age period and egg weight was lower during the 96 to 97 wk-of-age period. Consequently, egg mass was lower during both the 92 to 93 and 96 to 97 wk-of-age periods. Feed conversion was more favorable for the control-fed hens from 100 to 103 wk of age. Mortality was lower for the EcoCal-fed hens from 92 to 93 and 100 to 105 wk of age. Results from December 2006 through May 2007 presented in this paper show mostly transient differences in production parameters between the dietary regimens. Future analyses will help better determine or affirm the effects of the EcoCal diet.