A strategy for increasing the molecular weight of a polyester by lipase-catalyzed polymerization of a lactone and hydroxy acid was developed using azeotropic dehydration with toluene and a Dearn-Stark trap packed with molecular sieves. Thus, polycaprolactone (PCL) and poly(15-hydroxypentadecanoic acid) having number-average molecular weights of 81000 and 42000, respectively, were obtained by a 6-h polymerization at 70 degreesC.