Wild oat (Avena fatua L.) was removed at several stages of growth from flax (Linam usitatissimum L.) plots in 1964, 1965, and 1966. The flaxseed yield was reduced as the period of competition increased during each year. In 1965, competition from wild oat until the 4 to 5-leaf stage reduced the flaxseed yield 15.1% while competition until maturity reduced the yield 74.9%. The number of bolls/sq ft also was reduced as the period of competition increased; but the number of seed/boll, plants/sq ft, and the weight/1000 seed were not affected consistently by wild oat competition. Both the percent oil of flaxseed and the iodine number of the oil were reduced by wild oat competition, but not until the wild oat was in the heading stage and the flax was in the boll stage.