Poly(N-methyllaurolactam) (PNMLL) and its blends with poly(4-vinylphenol) (PVPh) were studied by a combination of infra-red, Raman and n.m.r. spectroscopic methods. In the crystalline phase of semicrystalline PNMLL, the amide bond was shown to be present in the cis form, and the polymethylene chain to contain long trans sequences, with a trans conformation on the -CH2-CO- bond. In the blends, the content of the crystalline phase, and also of the polymethylene trans sequences, is strongly suppressed. Analysis of the O-H stretching vibrations shows that in the blends the hydrogen bonds between the O-H groups of PVPh and PNMLL carbonyls are stronger than the hydrogen bonds in pure PVPh. The values of T-1 rho(H) relaxation times indicate intimate mixing of the blend components on a scale of <3 nm.