Polyurethanes may be able to replace biodegradable polyesters since the biodegradability and certain mechanical properties of polyurethanes can be adjusted by modifying their chemical structures. A prepolymer was prepared from poly(butylene succinate) diol (MW 1600) and 4,4'-methylenebis(phenyl isocyanate), and chain-extended with 2,2-bis(hydroxymethyl)propionic acid (DMPA). The resulting polyurethane (PU) was neutralized with a base to obtain polyurethane ionomers (PUIs). The thermal transitions of the PUIs were not much different from those of the PU. However, the mechanical strengths were greater than both the PU and a typical biodegrdable aliphatic polyester. For those PUIs in which the degree of neutralization with NaOH was 50% and 100%, the hydrolytic degradation was very rapid in a 5% NaOH solution at 37 ℃. Their weight loss was approximately 30 and 50% within 2 days, respectively, while the PU was degraded only about 15% under the identical conditions. Some polyesters (Mn 40000 and 80000) underwent a degradation of about 10-20%. Accordingly, this study suggests that the PUIs can be applicable to the fabrication of degradable plastic materials.