A process for preparing quaterrylene-3,4:13,14-tetracarboximides of the general formula I ##STR00001## in which R, R' are each independently hydrogen or optionally substituted C.sub.1-C.sub.30-alkyl, C.sub.5-C.sub.8-cycloalkyl or aryl or hetaryl; which comprises reacting a perylene-3,4-dicarboximide of the general formula IIa ##STR00002## in the presence of a base-stable, high-boiling, organic solvent and of an alkali metal base or alkaline earth metal base, with a perylene-3,4-dicarboximide of the general formula IIb ##STR00003## in which X is hydrogen, bromine or chlorine.