A high concentration herbicide concentrate composition having a viscosity of less than 0.14 kg m-1s-1 (140 centipoise) consisting essentially of: (a) water, (b) glyphosate, at least 50 percent in the form of the monomethylamine or dimethylamine salt, in solution in water in an amount of more than 350 grams of acid equivalent per liter of the composition, and (c) at least one surfactant in a total amount of 20 to 200 grams per liter of the composition, wherein the surfactant is (a) an alkylamine or alkyleteramine surfactant having the chemical formula in which R1 is a saturated or unsaturated linear or branched chain C8-C24 hydrocarbyl group, optionally interrupted by one or more ether bonds, and R2 and R3 are independently C1-C4 alkyl groups, or polyoxyalkylene chains having a total of 2 to 22 alkylene oxide units； (b) a quaternary ammonium surfactant having the chemical formula ** Formula ** in which Z- is an anion acceptable in agriculture, such as chloride, bromide, iodide, sulfate or acetate and R4, R5, R6 and R7 include, without limitation, the following: (i) R4 is a benzyl group or a saturated or unsaturated linear or branched C8-C24 hydrocarbyl group, optionally interrupted by one or more ether linkages, and R5, R6 and R7 are independently groups C1-C4 alkyl； (ii) R4 and R5 are independently a saturated or unsaturated C8-C24 straight or branched chain hydrocarbyl group, optionally interrupted by one or more ether bonds, and R6 and R7 are independently C1-C4 alkyl groups； (iii) R4 is a saturated or unsaturated C8-C24 straight or branched chain hydrocarbyl group, optionally interrupted by one or more ether bonds, R5 is a polyoxyalkylene chain having 2 to 22 C2-C4 alkylene oxide units, and R6 and R7 are independently C1-C4 alkyl groups； or (iv) R4 is a saturated or unsaturated C8-C24 straight or branched chain hydrocarbyl group, interrupted by one or more ether bonds, R5 and R6 are polyoxyalkylene chains having 2 to 22 C2-C4 alkylene oxide units , and R7 is a C1
