Compatible poly(trimethylene terephthalate) (PTT)/poly(hydroxy ether of bisphenol A) (Phenoxy) blends were obtained by direct injection molding throughout the composition range. Two amorphous phases with minor amounts of the other component were found in the blends. Reactions occurred in PTT-rich blends. By comparing the miscibility level of these blends with that of other blends based on polyalkylene terephthalates, it is proposed that a miscibility limit delimited by a 3/1 methylene-carbonyl ratio in the polyalkylene terephthalate exits in these blends. The synergism in the Young's modulus of the blends is discussed as a consequence of the changes in the crystallinity of PTT, the specific volume and the orientation produced by blending. Ductility is approximately proportional to blend composition, indicating compatibility, and is attributed to the combined effects of a small particle size and a good adhesion level, the latter being a consequence of the partially miscible nature of the blends. (c) 2006 Wiley Periodicals, Inc.