Condensation products of .epsilon.-caprolactam, formaldehyde and formamide, especially N-(formylaminomethyl)-.epsilon.-caprolactam and N-(N'-formyl-N'-hydroxymethyl-aminomethyl)-.epsilon.-caprolactam, are prepared by reacting formamide and formaldehyde in the presence of a base and in the presence or absence of .epsilon.-caprolactam at temperatures of 70.degree. to 90.degree. C. for 4 to 15 hours, then acidifying the reaction batch and, if no .epsilon.-caprolactam is present, adding .epsilon.-caprolactam, and distilling off water at 100.degree. to 135.degree. C.The condensation products are valuable modifiers for use in the manufacture of aminoplast resins employed for impregnating paper and fabrics which are used for the manufacture of coated wood-based materials and laminates.