A number of new aryl phosphorus-containing polymers were found to be miscible with the commercially significant bisphenol A-based poly(hydroxy ether)s (PHE) over the entire composition range by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) measurements of the blends. Both the FTIR and CP-MAS P-31 NMR results suggested extensive hydrogen-bonding interactions between hydroxyl groups and the phosphonyl groups. Specifically, the poly(arylene thioether diphenylphenylphosphine oxide) and phosphorus-containing polyimides were also miscible with PHE, again emphasizing the importance of phosphonyl groups for generating miscible polymer blends. In contrast, a structurally similar commercial polyimide, Ultem, was not miscible with PHE. These results suggested that the miscibility was induced mainly by hydrogen bonding between phosphonyl and hydroxyl groups, rather than other sites such as carbonyl or ether oxygen atoms and the hydroxyl groups. Furthermore, the measurements of proton spin-lattice relaxation times in the rotating frame (T-1 rho) showed that the phosphorus-containing polyimide/PHE blends were homogeneous even at about a 4 nm scale.