A herbicidal composition comprises an aqueous solution of one to a plurality of salts of glyphosate at a total glyphosate a.e. concentration not less than about 360 g/l, wherein (a) said glyphosate is in anionic form accompanied by low molecular weight non-amphiphilic cations in a total molar amount of about 110% to about 120% of the molar amount of said glyphosate; and (b) a major amount to substantially all of the low molecular weight non-amphiphilic cations are potassium cations. The composition exhibits improved tank-mix compatibility with a phenoxy-type herbicide salt formulation by comparison with an otherwise similar composition having a lower molar amount of said low molecular weight non-amphiphilic cations.