Although bioerosion can be caused by the solubilization of an intact polymer, chemical degradation of the polymer is usually the underlying cause for the bioerosion of a solid, polymeric device. Several distinct types of chemical degrada- tion mechanisms have been identified (Fig. 2) (Rosen et al., 1988). Chemical reactions can lead to cleavage of cross- links between water-soluble polymer chains (mechanism I), to the cleavage of polymer side chains resulting in the for- mation of polar or charged groups (mechanism II), or to the cleavage of the polymer backbone (mechanism III). Obviously, combinations of these mechanisms are possible: for instance, a cross-linked polymer may first be partially solubilized by the cleavage of crosslinks (mechanism I), followed by the cleav- age of the backbone itself (mechanism III). It should be noted that water is key to all of these degradation schemes. Even enzymatic degradation occurs in aqueous environment