The nutritive value of wild oats has been examined in two trials with growing rats. Feed consumption was reduced with diets containing 50 % wild oats and dry-matter digestibility was lower (76 and 73 %) with two diets containing 25 and 50 % wild oats compared with diets containing 25 and 50% barley (80-2 and 81-1 %). Live-weight gain was depressed when diets contained more than 45 % wild oats and it can be predicted that growth and feed conversion ratios of monogastric animals fed on diets containing high levels of wild oats are liable to be affected adversely. Biochemical studies indicated that any reduction in growth rate could not be attributed readily to specific toxic effects.