The dry fermentation of chicken manure (CM) for production of methane in mesophilic conditions at 37 degrees C was studied under laboratory conditions using a repeated batch culture system. Methane was successfully produced after an acclimation period of about 254 d. A total volume of 4.4 l kg(-1) CM (31 ml g(-1)VS) of methane gas was produced, despite the presence of a high level of ammonia of ca. 8 to 14 g-N kg(-1) CM. This clearly demonstrates that spontaneous acclimation of the methanogenic consortia to high levels of ammonia could occur and result in production of methane even under a high percentage of total solid (25%) and a high level of ammonia. (C) 2008, The Society for Biotechnology, Japan. All rights reserved.