AbstractCell walls of barley straw (whole sample and stem), Italian ryegrass (shoot) and lucerne (mature stem) were treated sequentially with NaOH followed by a commercial ‘cellulase’ preparation and, in other experiments, with the cellulase followed by the alkali. The phenolic compounds released by NaOH were determined and related to increases in the degradability of the walls as measured with cellulase. Two sequential treatments of the cell walls of barley straw increased degradability from 11% on treatment with cellulase alone to 87%, compared with increases from 72 to 99% and from 19 to 54% for the ryegrass and lucerne walls respectively. The first alkali treatment released ferulic andp‐coumaric acids from the walls of barley and ryegrass together with other u.v. absorbing compounds, whereas the compounds released by the second alkali treatment did not include these two acids. The treatment with alkali did not release either ferulic acid orp‐coumaric acid from the walls of lucerne and the amounts of other u.v. absorbing compounds that were released were much