The aim of this study was to evaluate the influence of metamitron dose and surfactant addition on weed control, phytotoxicity effect and yield of sugar beet. The herbicide was applied before crop emergence at full (recommended) dose and reduced by 33%. Additionally, reduced dose application was performed in the mixture with surfactant Trend 90 EC. The field experiments were carried out in the years 2008–2010, on arable fields located near Wrocław. The greatest weed control effect was obtained after application of metamitron at full dose. Reduction of the metamitron dose resulted in a decrease of herbicide efficacy against all weed species. The addition of surfactant to reduced dose of metamitron improved herbicide effectiveness to a level that was observed for the full dose of herbicide. The highest sugar beet yield was obtained when metamitron was applied at full dose alone and reduced dose in the mixture with surfactant. Significantly lower yield of sugar beet was harvested from plots treated with reduced dose of metamitron without surfactant.