The effect of inoculum source on anaerobic thermophilic digestion of separately collected organic fraction of municipal solid wastes (SC_OFMSW) has been studied. Performance of laboratory scale reactors (V: 1.1 L) were evaluated using six different inoculums sources: (1) corn silage (CS); (2) restaurant waste digested mixed with rice hulls (RH_OFMSW); (3) cattle excrement (CATTLE); (4) swine excrement (SWINE); (5) digested sludge (SLUDGE); and (6) SWINE mixed with SLUDGE (1:1) (SWINE/SLUDGE). The SC_OFMSW was separately and collected from university restaurant. The selected conditions were: 25% of inoculum, 30% of total solid and 55 degrees C of temperature, optimum in the thermophilic range. The six inoculum sources showed an initial start-up phase in the range between 2 and 4 days and the initial methane generation began over 10 days operational process. Results indicated that SLUDGE is the best inoculum source for anaerobic thermophilic digestion of the treatment of organic fraction of municipal solid waste at dry conditions (30% TS). Over 60 days operating period, it was confirmed that SLUDGE reactor can achieve 44.0% COD removal efficiency and 43.0% VS removal. In stabilization phase, SLUDGE reactor showed higher volumetric biogas generated of 78.9 mL/day (or 35.6 mL CH4/day) reaching a methane yield of 0.53 L CH4/g VS. Also, SWINE/SLUDGE and SWINE were good inoculums at these experimental conditions. (c) 2006 Elsevier Ltd. All rights reserved.