Poly (L-lactic acid) (PLA) is a biodegradable polymer with slow crystallization rate. Oligomers of 3-hydroxybutyrate (OHB) and dendrimers of hydroxyalkanoic acids with different molecular weights were blended with PLA in a hope to improve the crystallization ability and thermal stability of PLA, respectively. Four thermally-degraded PHB products oligomers termed OHB-1, OHB-2, OHB-3, and OHB-4 with various number average molecular weights (M-n) of 4000, 7400, 14,000, and 83,000, respectively, were blended with PLA. The lower cold-crystallization temperature (T-cc) and higher heat of cold crystallization (Delta H-cc) for blend of PLA/OHB-1 suggested that thermally-degraded OHB-1 formed suitable crystal size during the cooling process and then acted as nucleation agents for PLA in the subsequent heating process. On the other hand, for the blending systems of PLA/dendrimers of hydroxyalkanoic acids, no obvious change on the thermal properties was observed compared with pure PLA except an improved PLA thermal stability possibly resulted from the crosslinking effects of the dendrimers (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1720-1727, 2009