Thin films of both pure soluble collagen (CLG) and poly(vinylalcohol) (PVA) and mixtures of the two, ranging from 20-80% PVA composition were studied to test the effects of PVA content and of glutaraldehyde vapour cross-linking. Both the thermal and mechanical behavior and, in addition, proteolytic stability were clearly influenced by the ratio of CLG/PVA. The experimental results indicate that no thermodynamic compatibility occurs between the two homopolymers. However, there is evidence that strong interactions, probably due to hydrogen bond formation, occur between the biological and synthetic polymers. The interactions appear stronger in those films with a lower PVA content and which were not cross-linked. Both the thermal and biological stability are increased and there is an improvement of the mechanical properties. The mutual intermolecular influence appears to allow the attainment of a good mechanical compatibility between CLG and PVA.