In the absence of information on the value of treated straw as a component of the diets of finishing cattle a series of experiments was started in January 1982 to compare diets containing differing proportions of rolled mineralised barley (B) and treated spring barley straw (T) with a control ration of 75% mineralised barley (with extracted soya bean meal supplement (s)) and 25% untreated spring barley straw (U). Two treatments remained common throughout but the others were changed to widen the scope of the investigation. Fishmeal supplementation (F) was introduced as an additional factor in the third trial.