Abstract. Effect of the herbicides Stratos Ultra (1000 and 2000 ml/ha) and Pulsar 40 (1000 and 1200 ml/ha) on the degree of weed infestation and productivity of birds foot trefoil was studied in the experimental field of the IMSA-Troyan during the 2010-2012 period on light grey pseudopodzolic soil. It was found that the herbicide Pulsar 40 applied at the dose of 1200 ml/ha, had high selectivity and was suitable for foliar treatment at the 2-4 leaf stage of birds foot trefoil, its herbicidal efficacy reaching 65, 76 and 98% during the years. The herbicide Stratos Ultra applied at the two doses of 1000 and 2000 ml/ha, was more unstable with regard to the dry mass yield. The produced yields of dry mass varied within a greater range depending on the degree of weed infestation, shown herbicidal effect and meteorological conditions. The yield was influenced to a greater extent by the herbicide type and to a smaller one by the dose of its application.