Non-treated or steam-exploded straw in co-digestion with cattle manure was evaluated as a substrate for biogas production compared with manure as the sole substrate. All digestions were performed in laboratory-scale CSTR reactors (5L) operating with an organic loading late of approximately 2.8g VS/L/day, independent of substrate mixture. The hydraulic retention was 25days and an operating temperature of 37, 44 or 52°C. The co-digestion with steam exploded straw and manure was evaluated with two different mixtures, with different proportion. The results showed stable performance but low methane yields (0.13-0.21NLCH4/kg VS) for both manure alone and in co-digestion with the straw. Straw appeared to give similar yield as manure and steam-explosion treatment of the straw did not increase gas yields. Furthermore, there were only slight differences at the different operating temperatures.