Imidazolines substituted in the 2-position are obtained by condensing N : N1-ethyleneurea, or an N : N1-ethyleneurea substituted at a carbon atom by a hydrocarbon radicle, with a monocarboxylic acid other than formic acid, the reaction occurring with elimination of water and carbon dioxide. In a typical example, N : N1-ethyleneurea and oleic acid, heated to 280-300 DEG C., yield 2-heptadecenyl-imidazoline. Examples are given also of the manufacture of imidazolines from N : N1-ethyleneurea and stearic acid, palmitic acid, benzoic acid, butyric acid, a - and b -naphthoic acids, diphenyl-4-carboxylic acid, carbazole-2-carboxylic acid, and an acid (molecular weight 238) obtained by the oxidation of paraffin. In a further example, N : N1-propylene urea is heated with benzoic acid to yield a mixture of 4- and 5-methyl-2-phenylimidazolines. Carbazole-2-carboxylic acid is obtainable by fusing 2-chloracetyl-N-acetylcarbazole with caustic potash.