Directly starting from lactic acid (LA) and poly(ethylene glycol) (PEG), biodegradable material polylactic acid-polyethylene glycol (PLEG) was synthesized via melt copolycondensation. The optimal synthetic conditions, including prepolymerization method, catalyst kinds and quantity, copolymerization temperature and time, LA stereochemical configuration, feed weight ratio M-LA/M-PEG and M,, of PEG, were all discussed in detail. When D,L-LA and PEG (M-n = 1000 Da) prepolymerized together as feed weight ratio M-D,M-L-LA/M-PEG = 90/10, 15 h copolycondensation under 165 degrees C and 70 Pa, and 0.5 wt % SnO as catalyst, gave D,L-PLEG1000 with the highest [eta] of 0.40 dL/g, and the corresponding MW was 41,700 Da. Using L-LA instead of D,L-LA, 10 h polymerization under 165 degrees C and 70 Pa, and 0.5 wt % SnO as catalyst, gave L-PLEG1000 with the highest [eta] of 0.21 dL/g and MW of 15,600 Da. Serial D,L-PLEG with different feed weight ratio and M, of PEG were synthesized via the simple and practical direct melt copolycondensation, and characterized with FTIR, H-1 NMR, GPC, DSC, XRD, and contact angle testing. D,L-PELG not only had higher MW than PDLLA, PLLA and L-PELG, but also better hydrophilicity than PDLLA. The novel one-step method could be an alternative route to the synthesis of hydrophilic drug delivery carrier PLEG instead of the traditional two-step Method using lactide as intermediate. (c) 2006 Wiley Periodicals,, Inc.