We propose a framework to describe the mechanical behavior of thermally damaged biological soft tissues based on a melding of ideas from classical continuum thermodynamics and irreversible thermodynamics. Relevant assumptions are delineated, details of the constitutive formulation are provided, and a set of interfacial conditions are derived that can be used as the boundary conditions for certain diffusion processes. The utility of the framework is illustrated by considering two problems that correspond to tractable experiments: transverse diffusion through a finitely deformed membrane, and radial diffusion in a thermally damaged cylindrical tissue. © 2001 Elsevier Science Ltd.