This study evaluated the technical feasibility of anaerobic co-digestion of three organic solid wastes under mesophilic conditions: organic fraction of municipal solid waste (OFMSW), industrial sludge (IS) and cattle manure (CM). Different proportions of each substrate were used and the results showed that, in general, the increase of OFMSW in the mixture results in higher methane production and volatile solids reduction. However, the co-digestion of OFMSW with another co-substrate, especially with IS, significantly improved the stability and process performance, with an effective decrease on the need for buffer addition. At mesophilic conditions and 5% of total solids (TS) inside the reactor, the optimum mixtures accessed from response surfaces obtained with the application of the mixture design technique were the binary mixture with 77% of OFMSW and 23% of IS for volatile solids reduction (65%) and also a binary mixture with 86% of OFMSW and 14% of IS for methane production (225 m(CH4)(3) ton(TVS)(added)(-1)). A good agreement was obtained between the response surfaces and experimental results, which allows the establishment of management strategies for handling these organic wastes in future. (c) 2007 Elsevier Ltd. All rights reserved.