Many　synthetic　and　natural　media　which　are　often　described　as　multifunctional　smart　materials　demonstrate　thermo-electro-chemo-mechanical　coupling　behavior　and　are　sensitive　to　external　environmental　stimuli.　This　paper　presents　a　set　of　basic　equal　ions,　a　variational　principle　and　a　finite　element　procedure　for　investigating　the　coupled　behavior　of　thermo-electro-chemo-elastic　media.　Emphasis　here　is　placed　on　introducing　chemical　effects　into　the　coupled　equation　system.　Using　the　governing　equations　of　thermal　conduction,　electric　flow,　ionic　diffusion　and　momentum　balance,　a　variational　principle　is　deduced　for　a　linearly　coupled　system　by　means　of　the　extended　Gibb＇s　free　energy　function.　The　variational　principle　is　then　used　to　derive　a　fully　coupled　multi-field　finite　element　formulation　for　simulating　the　coupled　thermo-electro-chemo-elastic　behavior　of　biological　tissues.　Numerical　examples　are　considered　to　illustrate　the　coupled　phenomena　of　the　materials　and　to　verify　the　proposed　variational　theory　and　numerical　procedure.　(C)　2009　Elsevier　Ltd.　All　rights　reserved.