Abstract: Proposed is a thixotropic agent for alkyd resins comprising the reaction product of an alkyd resin and a poly(ester)amide obtained by reacting a polycarboxylic acid with a compound of the formula Xm—R—Yn, wherein R stands for an organic group having at least 2 carbon atoms, X and Y may be the same or different and stand for a primary or secondary amino group or a hydroxyl group, and m and n are each at least equal to 1, with at least 50 mole % of the polycarboxylic acid being a dimeric fatty acid having at least 36 carbon atoms, wherein in at least 25 mole % of the compound of the formula Xm—R—Yn R stands for a substituted or unsubstituted aromatic group having 6 to 18 carbon atoms and X and Y may be the same or different and stand for a primary or secondary amino group, and in at most 75 mole % of the compound of said formula R stands for a substituted or unsubstituted aliphatic group having 2 to 54 carbon atoms, an araliphatic group having 7 to 18 carbon atoms and/or an aromatic or c