Cotton straw (CS) and cotton straw stored as silage-like materials (CSS) were treated with alkaline peroxide solution, using either NaOH or CaO (lime) as a source of alkali, in order to increase its biodegradability. A 50-58% reduction in the lignin content was reflected by a twofold increase in the E280 of the reaction solution. In-vitro organic matter digestibility increased from 16 to 20% in untreated material to 61-64% after the treatments. Although the extent of delignification was greater when NaOH was used as a source of alkali, in-vitro dry matter digestibility of the treated straw was similar for the two treatments.