A new biodegradable poly(L-aspartic acid-co-poly(ethylene glycol)) having pendant amine functional groups was synthesized by the melt polycondensation reaction of prepolymer prepared from N-(benzyloxycarbonyl)-L-aspartic acid anhydride (N-Z-L-aspartic acid anhydride) and poly(ethylene glycol). The synthesized polymer was characterized by FTi.r., H-1 n.m.r., d.s.c., g.p.c. and solubility. The weight-average molecular weight of the prepolymer increased about 11 times via melt polycondensation at 160 degrees C in a vacuum for <1 h.