The structures of four isomeric compounds, all C7H4ClNO4.C9H7N, of quinoline with chloro- and nitro-substituted benzoic acid, namely, 2-chloro-5-nitrobenzoic acid-quinoline (1/1), (I), 3-chloro-2-nitrobenzoic acid-quinoline (1/1), (II), 4-chloro-2-nitrobenzoic acid-quinoline (1/1), (III), and 5-chloro-2-nitrobenzoic acid-quinoline (1/1), (IV), have been determined at 185 K. In each compound, a short hydrogen bond is observed between the pyridine N atom and a carboxyl O atom. The N...O distances are 2.6476 (13), 2.5610 (13), 2.5569 (12) and 2.5429 (12) A for (I), (II), (III) and (IV), respectively. Although in (I) the H atom in the hydrogen bond is located at the O site, in (II), (III) and (IV) the H atom is disordered in the hydrogen bond over two positions with (N site):(O site) occupancies of 0.39 (3):0.61 (3), 0.47 (3):0.53 (3) and 0.65 (3):0.35 (3), respectively.