Miscibility of poly(N,N-dimethylacrylamide) (PDMA) with poly(vinyl acetate) (PVAC), poly(vinyl alcohol) (PVAL) and poly(vinyl acetate-co-vinyl alcohol) (ACAL copolymers) has been investigated over a wide composition range. Differential scanning calorimetry (DSC) results indicate that PDMA is immiscible with PVAC, but is miscible with PVAL and ACAL copolymers in certain range of compositions. The ACAL/PDMA phase diagram for different copolymer compositions has been determined. The variation of the glass transition temperature with blend composition for miscible systems was found to follow the Kwei equation. Infrared spectroscopy studies of blends reveal the existence of specific interactions via hydrogen bonding between hydroxyl groups in vinyl alcohol units and the carbonyl group in the tertiary amide, which appear to be decisive for miscibility.