Stable, concentrated solutions of complex metal compounds of azo dyestuffs

A stable, concentrated substantially anhydrous solution of a metal complex azo dyestuff, wherein the solution contains 10 to 60% by weight of at least one heavy metal complex azo or azomethine dyestuff containing a sulfonic acid group, dissolved in 90 to 40% by weight of at least two water-miscible, organic solvents which are liquid at room temperature, selected from the group consisting of mono or polyalkylene glycol or thioglycol or ether thereof, a hydroxylated ketone, a cyclic ether, a lactam, lactone, dimethyl sulfoxide, sulfolan, sulfolene, hexamethylphosphoric acid triamide, dimethyl methyl phosphonate, N-methylpyrrolidone and a low molecular aliphatic carboxylic acid amide.