The efficacy of nicosulfuron on 'Setaria glauca' (yellow foxtail) and 'Setaria viridis' (green foxtail) was compared in both field and growth room studies. Nicosulfuron was tested at 6.25, 12.5, and 25 gai/ha with four different concentrations of non-ionic surfactant (0, 0.1, 0.2 and 0.4% v/v). Results showed similar trends in both the field and growth room studies. Regardless of rates of nicosulfuron or of non-ionic surfactant tested, control of green foxtail was consistently higher than yellow foxtail. Uptake, translocation and metabolism of nicosulfuron were evaluated in both species. Results indicated that uptake of nicosulfuron by green foxtail was greater than that of yellow foxtail, though the difference in uptake decreased between the two species with higher rates of non-ionic surfactant. Translocation and metabolism of nicosulfuron was similar for both species.