Porous membranes composed of the biodegradable polyesters poly(D,L-lactide) (PLA) and poly(D,L-lactide-co-glycolide) (PLGA) were prepared by a phase inversion process. The molecular weights of the polymers and the concentrations of the polymer solutions affected the pore size and structure of the PLA and PLGA membranes. The molecular weights and morphological changes of the membranes as a function of time were investigated under incubation at 37 degreesC in a humidified 5% CO2 atmosphere. The pores that formed in the membranes changed dramatically with increasing time under these conditions. From the thermal characterization of the polymers in their dry and wet states, we found that the glass-transition temperatures of PLA and PLGA affected morphological structure changes in the porous membranes. We also prepared a collagen-coated membrane to improve the interaction between the cell and the substrate, and we observed that the collagen coating enhanced the attachment and growth of Chinese hamster ovary cells on the substrate. Finally, we found that only PLA was a suitable material to prepare a porous membrane scaffold with the phase inversion process with PLA, and a collagen coating was necessary for cell culture on the membrane. (C) 2004 Wiley Periodicals, Inc.