A series of aregic poly(ester amide)s (a-PEAT6) with ester/amide ratios (a : b) varying from 1 : 19 to 1 : 2 were prepared with L-tartaric acid, 6-aminohexanol, and 1,6 hexanediamine as the starting materials. Polycondensation in a solution of the diamine with mixtures of pentachlorophenyl-activated di-O-methyl-L-tartaric and 6-aminohexyl-di-O-methyl-L-tartaric acids led to a-PEAT6(a : b), with the a : b ratio determined by the composition of the feed. The newly synthesized poly(ester amide)s were characterized by elemental analysis, size exclusion chromatography, and IR and NMR spectroscopy. They had number-average molecular weights between 25,000 and 45,000 and were highly crystalline, showing melting temperatures ranging from 100 to 230 degrees C and glass-transition temperatures oscillating between 50 and 100 degrees C. The thermal degradation of a-PEAT6(a : b) began above 200 degrees C and concluded with a final weight loss between 60 and 90% of the initial mass. The process evolved with the formation of cyclic tartarimide units and extensive main-chain scissions. The degradation mechanism is discussed in relation to the chemical composition and microstructure of the polymers.