A EDUSAHEAD, Elymus caput-medusae L., an exotic winter annual lVl grass, was introduced into northeastern Washington and probably adjacent Idaho over 50 years ago (6). Official records show its presence in southwestern Idaho 15 years ago, but ranchers in this area assert that it was present 25 to 30 years ago. Prior to 1950 it was known to infest a few thousand acres in southwestern Idaho and its distribution from 1945 to 1950 appeared rather static. Since 1950, medusahead has become alarmingly aggressive. Estimates of the infested area in southwestern Idaho have increased from 20,000 acres in 19524 to 700,000 acres in 1958.5 In a decade its position has changed from a minor problem to one of major concern to the range livestock industry. This problem is three-fold: first, it suppresses desirable vegetation due to its competitive ability; second, it is unpalatable to livestock at all stages of growth; and third, the dead vegetation decomposes slowly, thereby forming a persisting dense duff layer on the soil surface. In addition, as the plant matures it develops long barbed awns which cause mechanical injury to the eyes, noses, and mouths of grazing animals. Medusahead is invading vast acreages formerly dominated by perennial grass species and more recently by downy bromegrass, Brornus tectorum L. The latter, although not a desirable range grass, provides considerable early spring forage. The growth habits, life cycles, and ecological adaptation of these two species appear to be similar. They typically grow in association until medusahead becames dominant and eventually exclusive. No previous research has been reported on the composition of medusahead. Palatability differences of the two species stimulated studies on their comparative chemical composition and on methods to improve livestock utilization of medusahead. Such studies might reveal factors which could influence palatability and nutritive value. Data on the chemical composition of downy brome and many other grass species were previously available (4).