Eight poly(phosphate ester)s comprising five homopolymers (polymers I-V), two copolymers (polymers VI and VII), and one terpolymer (polymer VIII) were synthesized by interfacial polycondensation of phenyl phosphorodichloridate with various bisphenols. The polymers were characterized by spectroscopic techniques. The copolymer and terpolymer ratios were determined by H-1-NMR spectroscopy. The molecular weights of the polymers were determined by end-group analysis using P-31-NMR spectroscopy. Accelerated hydrolytic degradation studies under alkali-catalyzed conditions showed that the polymer from biphenol (polymer IV) is the most stable and the polymer from thiodiphenol (polymer V) is the least stable. The products of hydrolytic degradation were analyzed and a suitable mechanism for the degradation of the polymers proposed.