Nitrogen-containing condensation products based on unmodified or modified natural resins, process for the preparation thereof and the use thereof.The invention relates to surface-active agents of the general formulaA--[(X--O).sub.n --Y--Z].sub.min which A is a radical of an unmodified or modified natural resin or esterification product thereof with a polyhydric alcohol, X is 1,2-ethylene or -propylene, Y is as defined for X or is --CH.sub.2 CHOHCH.sub.2 --, Z is OH or (Ia)(--NH--Q).sub.a --NR--(Q--NH--).sub.b H (Ia)in which R is H or C.sub.1 -C.sub.24 --alkyl or (--CH.sub.2 CH.sub.2 O).sub.p --H, with p being 1 to 100, or (--Q--NH).sub.c --H, Q is C.sub.1 -C.sub.24 ---alkylene which can be interrupted by oxygen atoms, a is 0-5 and c is 0-5,at least one Z being other than OH,n is 0 to 150 andm is 1 to 5.The compounds are obtained by alkoxylating resins or esterification products thereof with polyhydric alcohols and, after conversion of hydroxyl groups into suitable leaving groups, reacting the products of with amines of the formula Z-H.The products are suitable above all as coupling auxiliaries, dispersants and formulating agents for colorants.