Solid state fermentation of chopped sweet sorghum particles to produce ethanol was studied statically using thermotolerant yeast. The influence of various process parameters, such as yeast cell concentration, particle size and moisture content, on the ethanol yield was investigated. Optimal values of these parameters were 4 x 10(6) cells/g raw sorghum, Dp = 1.5 mm and 75%, respectively. Addition of reducing agent H2SO3 into the fermentation medium provided anaerobic condition, and obtained the maximum ethanol yield of 7.9 g ethanol per 100 g fresh stalks or 0.46 g ethanol/g total sugar, which was 91% of the theoretic yield. (C) 2008 Elsevier B.V. All rights reserved.