Wheat straw is the principal raw material for edible mushroom substrate preparation in Europe and America. The knowledge of its biodegradability by saprotrophic microorganisms is useful. By combining an enzymatic method with simple chemical analyses 29 samples of straw were distinguished in a principal component analysis. The effects of genetical variations, of cultivation practices and of sites of cultivation were observed. The measurement of the in vitro degradability of polysaccharides was the most discriminative variate with the two first principal components. Correlations between the measurements were determined with 52 straw samples and a practical simplified method was proposed. It includes ash content, water soluble compounds and the in vitro degradability of polysaccharides measured with a mixture of polysaccharidases. The significance of these measurements was investigated and discussed.