Biodegradable poly(L-aspartic-acid/valine) (PAV) was synthesized by thermal polycondensation. The molar ratios of aspartic acid/valine were 9 : 1, 8 : 2, 7 : 3, 6 : 4, and 5 : 5, respectively. The chemical structure of PAV was confirmed by C-13-NMR, DSC, FTIR, X-ray, and GPC measurements. The degradation of PAV was studied in PBS buffer solution (pH 7.4 and 8.2) and in aqueous solution with enzymatic hydrolysis in which papain and trypsine acted as catalyst. It showed that the, biodegradation rate of PAV was increased when the content of valine in copolymer increased. 3-Hydroproplamine was used in a succinimide ring-open reaction to obtain hydrophilic products (PHPAV). Stability tests showed that humidity, light, and temperature had no remarkable effect on PHPAV, however, it could be degraded in base solution. Biocompatibility and hematological tests were investigated. No deaths were found in the mice treated with PHPAV solution up to a 7.5 g/kg dose. No differences in number of red cells and glutamic pyruvic and creatinuria transaminase activities were found between the experiment and the control groups. (c) 2006 Wiley Periodicals, Inc.