The miscibility of blends of nylon 6 with poly(maleic anhydride-co-vinyl acetate) (poly(MAH-co-VAc)), or hydroxylated poly(maleic anhydride-co-vinyl acetate) (poly(MAH-co-VAc)H) was investigated by means of Fourier transform infra-red (FTi.r.) spectroscopy, differential scanning calorimetry (d.s.c.), and X-ray diffraction. Poly(MAH-co-VAc) was prepared by radical copolymerization and the copolymers were hydrolysed to form poly(MAH-co-VAc)H at reflux temperature in H2O. Poly(MAH-co-VAc) and poly(MAH-co-VAc)H were characterized by FTi.r. and H-1-n.m.r. spectroscopy. On the basis of optical clarity, glass transition temperature (Tg), FTi.r. spectra, and X-ray diffraction, it was found that the nylon 6/poly(MAH-co-VAc) blends showed immiscible behaviour over the entire blend concentration but the poly(MAH-ca-VAc)H showed miscibility with nylon 6 over blend concentrations above 75 wt% of poly(MAH-co-VAc)H. The FTi.r. results showed that strong specific interactions between the carboxylic acid group of poly(MAH-co-VAc)H and the amide group of nylon 6 are responsible for the miscibility.