Newly developed herbicides such assulfosulfuron or sulfosulfuron plus metsulfuron-methyl may control wild barly at higher rate than recommended dose. But causing significant wheat injury. Hence, two dose-response experiments were conducted to evaluate their efficacy when tank-mixed with thirteen different vegetable oils at Research greenhouse, College of Agriculture, Ferdowsi University of Mashhad-Iran, . A wheat cultivar (Gaskogen) was also treated with 90% effective dose (ED90) of both herbicides (21.44 g a.i. of sulfosulfuron ha-1 and 41.95 g a.i. of sulfosulfuron plus metsulfuron-methyl ha-1) with and without each vegetable oil to check selectivity. Averaged over vegetable oils, the effective dose 50% (ED50)was decreased 2.6- and 2.0-fold with sulfosulfuron and sulfosulfuron plus metsulfuron-methyl, respectively. Among evaluated the vegetable oils, both cottonseed oil and coconut oil were the best to enhance the efficacy of both herbicides. Whears, the castor oil had the least effect. A negative correlation was observed between the efficiency of vegetable oils and its unsaturated/saturatedfatty acids ratio. The phytotoxiceffect on wheat did not observe when they were appliedwith and without vegetable oils.

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