Ammonia suppressants are applied to chicken litter to decrease ammonia levels. And mushroom (Agaricus bisponts) producers use poultry litter to increase the nitrogen in the compost. To determine the influence of ammonia suppressants used in Poultry litter on compost preparation and mushroom production, four mushroom crops were cultivated from compost prepared using litter treated ,/100 with PLT, Barn Fresh and Impact-P at 25.22 kg/100 m(2) 40 kg/100 m(2) and 0.49 kg/100 m(2), respectively, during the poultry production process. In general, no significant differences (P > 0.05) were noted between treatments for total nitrogen, ammonia. pH. EC, ash, and moisture when compost or the headspace air was sampled during compost preparation throughout all stages. Nor were mushroom yields or counts significantly affected (P > 0.05) by the presence of ammonia suppressants in the poultry litter. Thus. the mushroom industry can confidently use poultry litter amended with PLT, Impact-P, and Barn Fresh when used at the recommended rates. (c) 2005 Elsevier Ltd. All rights reserved.