Research was conducted to determine the effect of nonionic surfactant properties on herbicide phytotoxicity to green foxtail. Herbicides evaluated were commercially formulated imazethapyr, nicosulfuron, quinclorac, rimsulfuron, and sethoxydim. Hydrophilic: lipophilic balance (HLB) was the only surfactant property that affected phytotoxicity enhancement of imazethapyr, quinclorac, rimsulfuron, or sethoxydim. Surfactant enhancement of nicosulfuron was affected by surfactant HLB, cloud point temperature, and pour point temperature. Optimum octoxynol HLB value for sethoxydim enhancement was 13.4 and for imazethapyr, nicosulfuron, quinclorac, and rimsulfuron between 15 and 16. Surfactants having similar HLB values but different chemistry differed in their enhancement of herbicide phytotoxicity to green foxtail. Surfactant efficacy was herbicide dependent. The results of these experiments indicate that surfactant efficacy is determined by the physical and chemical properties of the surfactant and the herbicide.