The use of compounds of the general formula I where A is ═N— or ═CH—; X when A is ═N— is methyl or a radical of the formula IIa or when A is ═CH— is an R radical; Y is an R radical or a radical of the formula IIb with either X being a radical of the formula IIa or Y being a radical of the formula IIb; R is hydrogen, halogen, C1-C4-alkyl, —SO3H, —SO3−Me+, —SO3−N+R1R2R3R4, —SO2NR1R2, —CH2NR1R2, —CH2R5, —COOH, —COO−N+R1R2R3R4, —COOR6 or —COR6; R1, R2, R3 and R4 are each independently hydrogen; C1-C22-alkyl or C2-C22-alkenyl whose carbon chain may in either case be interrupted by one or more —O—, —S—, —NR7—, —CO— or —SO2− moieties and/or which may be substituted by one or more of hydroxyl, halogen, aryl, C1-C4-alkoxy and acetyl; C3-C8-cycloalkyl whose carbon skeleton may be interrupted by one or more —O—, —S—, —NR7— or —CO— moieties and/or which may be substituted by one or more of hydroxyl, halogen, aryl, C1-C4-alkoxy and acetyl; hydroabietyl, abietyl or aryl; R1 and R2 or R1, R2 and R3 may combine to form a 5- to 7-membered cyclic radical which contains the nitrogen atom and may contain further hetero atoms; R5 is a radical of the formula IIb′ R6 is one of the R1 alkyl radicals; R7 is hydrogen or C1-C4-alkyl; Me is an alkali metal ion; Z and Z′ are each independently arylene which may be substituted by one or more of halogen, —SO3H, —SO3−Me+, —SO3−N+R1R2R3R4, and C1-C12-alkyl, and the rings B1 and B2 may each be independently additionally substituted by one or more identical or different R radicals other than hydrogen, as crystallization modifiers for organic pigments.