The reaction of N1-phenyl- and N1-(4-methoxyphenyl)benzene-1,4-diamines with maleic anhydride gave the corresponding maleic acid monoamides whose cyclization in the presence of p-toluenesulfonic acid afforded 1-[4-anilino- and 4-(4-methoxyanilino)phenyl]-1H-pyrrole-2,5-diones.