The inheritance in oats of reaction to some new races and to some well-known races of oat stem rust, Puccinia graminis Pers. f. sp. avenae Erikss. and Henn., was investigated in the crosses Jostrain × Eagle, Canuck × Cherokee, and R.L. 524.1 (Hajira × Banner) × Eagle. The resistance of the variety Jostrain to races 1, 3, 4, 13, and 13A was conferred by a single gene, here designated as the E gene in accordance with the practice of designating genes for stem rust resistance by capital letters. Canuck, a derivative of Jostrain, carries the new E gene and the previously identified B gene. The resistance of R.L. 524.1 to all races is conferred by two major genes and a modifying gene. One of the major genes acts like the well-known B gene which confers resistance to all races except 6A, 7A, 8A, and 13A. The other major gene apparently is a new gene in oats for resistance to stem rust and is here designated the F gene. The F gene confers resistance to all races but a modifying gene is required along with it for resistance to race 7.