The genetics of resistance against powdery mildew in flax was analyzed.The F1 plants from reciprocal cross of resistant materials 9801-1 and three susceptible cultivars ILONA,VENUS and DIANE were resistant to powdery mildew.The ratio of resistant and susceptible plants in F2 generation fitted the excepted 3 to 1.It was postulated that 9801-1 carried a single dominant and resistant gene.