Abstract: Process for the bath pigmentation of leather, which comprises dyeing the leather with pigment dispersions which contain a compound of the formula (I) ##STR1## where Ar is benzene or naphthalene,X is --CH.sub.2 --CH.sub.2 -- and/or --CH.sub.2 --CH(CH.sub.3)--,0 to (m-1) of the radicals A are hydrogen,1 to m of the radicals A are benzoyl and/or naphthoyl,1 to m of the radicals A are --CO--CH.dbd.CH--COOM and/or --CO--CH.sub.2 --CH(SO.sub.3 M)--COOM, where M is a cation,R.sup.1, R.sup.2 and R.sup.3 are hydrogen or alkyl of 1 to 14 carbon atoms,R is hydrogen and/or alkyl of 1 to 9 carbon atoms, n is a number from 1 to 150 and m is a number from 2 to 12,The pigment having an average particle size of 50 to 500, preferably 80 to 300, nm. By using these dispersions, which contain the pigments in a very finely divided form, it is possible to obtain thorough penetration of the leather with improved light fastness.