The aim of the study was to estimate the optimal harvest time and overall potential of barley straw and reed canary grass (RCG) as feedstocks for bio-ethanol production. The estimate was conducted based on samples from field trials in Finland collected during the seasons 2005/06 and 2006/07. The total dry matter (DM) yield for barley was 8-10 metric tons ha -1 , whereof proportion of straw comprised 30%. For RCG the highest DM yield, more 11 tons ha -1 , was obtained one month after seed maturing. The content of soluble sugars decreased drastically when plant got older being the lowest in mature barley straw and in dead plants in spring for RCG. Cellulose and lignin content of barley straw increased until dough stage of grain and changed only slightly thereafter. Changes in hemicellulose content were equal but lesser. Cellulose and lignin content for RCG was higher the later the plant material was harvested. Only minor changes in hemicellulose content were discovered. Barley straw taken at harvesting time, and RCG taken at seed maturing time and in spring were treated by steam explosion, where after the success of enzymatic hydrolysis and yeast fermentation were evaluated in laboratory-scale. The enzymatic hydrolysis of steam exploded washed raw materials followed by yeast fermentation was evaluated in laboratory- scale. Both RCG and barley straw were easily pre-treated with steam explosion, hydrolysed to monosaccharides and fermented to ethanol, and thus suitable raw materials for ethanol production.