We investigated hydrogen production by fermentation of enzymatic hydrolysates of Avicel and xylan, using Clostridium sp, strain no. 2. At 0.3% concentration in peptone yeast (PY) medium, pure xylose or glucose and crude hydrolysates of Avicel or xylan were converted to hydrogen at yields of 16.1 mmol or 14.6 mmol and 19.6 mmol or 18.6 mmol, per gram of substrate consumed, respectively. Alternatively, a batch culture of strain no. 2 grown in PY medium containing 1% of xylan or xylose with crude xylanase preparation and xylose alone as a reference, gave hydrogen production of 9.5 mmol or 9.6 mmol and 10.3 mmol, per gram of substrate supplemented, respectively.