Many problems involve effects that interconnect in particular ways and interfere with each other to form distinctive coupling. In other problems, coexisting effects can be considered to be decoupled. This chapter discusses problems related to heat conduction and thermal stress in solids. Generally, effects of heat conduction and thermal stress can be decoupled because the orders of magnitude of characteristic times for these effects differ considerably. The chapter discusses heat conduction, introduces a thermal stress–strain relationship and discusses the similarity law for thermal stress in solids.