In greenhouse tests, temperature, humidity, drought stress, and concentration of surfactant influenced the foliar activity of spray mixtures containing a dodecyl ether of polyethylene glycol (Surfactant WK) and 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (diuron) or 3-(3,4-dichlorophenyl)-1-methoxy-1-methyl urea (linuron). In comparisons with other commonly used surfactants, Surfactant WK gave a superior performance when used in conjunction with diuron, linuron, and 5-bromo-3-sec-butyl-6-methyl uracil (bromacil). Increased water solubility of these herbicides in the presence of surfactant is only one factor among many involved in the enhanced activity of such combinations. Surfactant WK facilitated the deposition of high concentrations of linuron on leaf surfaces of Johnsongrass. Once a gradient was established, subsequent rapid movement of the herbicide into the leaf was noted.