2-(4-Carboxyphenyl)-1,3-oxazoline (2a), 2-(3-carboxyphenyl)-1,3-oxazoline (2b), and 2-(6-carboxynaphthyl-2-yl)-1,3-oxazoline (2c) were synthesized by reaction of monomethyl ester chlorides of aromatic dicarboxylic acids with 2-chloroethylamine hydrochloride in the presence of triethylamine followed by cyclization with methanolic KOH. Thermal polymerization in bulk within a few minutes at 200-220 degrees C resulted in new linear poly(ester amide)s 3a-3c without significant side reactions. The polymerization occurred in the melt phase (2b) or in the solid state (2a, 2c) and the resulting polymers are amorphous (3b) or semi-crystalline (3a, 3c). The polyaddition reactions were investigated by means of differential scanning calorimetry (DSC) and H-1 NMR spectroscopy.