A series of aregic poly(ester amide)s (ar-PEALM) with ester to amide groups ratios (a:b) ranging from 1:50 up to 1:2 were prepared from O-methyl-L-malic acid, 1,6-hexanediol, and 1,6-hexanediamine. The ester linkage was incorporated in the poly(ester amide) chain using 6-aminohexyl-pentachlorophenyl O-methyl-L-malate as comonomer in the polycondensation of bis(pentachlorophenyl) O-methyl-L-malate with 1,6-hexanediamine. The polycondensation of the amino ester alone afforded isoregic ir-PEALM (1:1) with both the amino alcohol and the malic units oriented in a unique manner along the polymer chain. The composition of ar-PEALM was found to be close to that of the feed used for polycondensation, with the diamine units incorporated in slight excess. The molecular weights of PEALM roughly oscillated between 10 000 and 50 000. All the poly(ester amide)s were semicrystalline with T-m decreasing with the content in ester groups from 168 to 144 degreesC and T-g falling down in parallel from 60 to 10 degreesC. The thermal decomposition of PEALM initiated around 260 degreesC and proceeded through a mechanism involving an intramolecular amidolysis reaction with generation of N-substituted cyclic malimides. PEALM poly(ester amide)s were easily degraded in water at pH 7.4, 37 degreesC, at a rate that increased with the content in ester groups. The hydrolytic process was found to occur preferentially on the ester linkages and to involve also the occurrence of intramolecular amidolysis reactions.