Smooth bromegrass, Bromus inermis, and red fescue, Festuca rubra, were sown in 1952 on a fertile soil severely infested with yellow toadflax, Linaria vulgaris Mill., in the Peace River section of Alberta. Annual applications of 2,4-dichlorophenoxyacetic acid (2,4-D) were made at late flower-bud stage at nil, 1, 2, 3, and 4 lb/A acid equiv. In 1958, the average per cent of toadflax in the brome was 1, 0.5, 0.5, 0, and 0, respectively. Red fescue had 6 to 0.1% of toadflax. All rates of 2,4-D prevented seed production. The sods were broken in 1959, and toadflax re-established strongly on all plots from dormant seed and residual plants. In 1961, the brome, rejuvenated by breaking, strongly suppressed toadflax, while fescue failed to compete with it.