Two hundred and two collections of non-cultivated oats from Israel, belonging to Avena sterilis L. and A. barbata Brot., were tested in the greenhouse at Winnipeg, Manitoba, for seedling and adult plant reaction to several important crown rust and stem rust races. Seeds of the collections found resistant in the greenhouse to one of the test races were planted in the field and were exposed to artificial rust epidemics. Out of 123 collections of A. sterilis, 40 were resistant to crown rust in the greenhouse and 9 remained resistant in the field; one collection was resistant to stem rust in the greenhouse but none was resistant in the field. Out of 79 collections of A. barbata, 23 were resistant to crown rust in the greenhouse and 8 maintained resistance in the field; 17 collections were resistant to stem rust in the greenhouse and 8 were resistant in the field.Crown rust and stem rust resistance factors seem to be independent of each other; the plants of only a few collections possessed resistance to both rusts. Collection D203 was particularly outstanding, showing resistance to all the test races of crown rust and stem rust in seedling and adult stages in the greenhouse as well as in the field.