We systematically analyze the stress‐strain‐temperature relationships and include thermal strain contributions to the misfit‐strain only formalism of strained‐layer heterostructures. Application of this theory to the GexSi1−x/Si (100) and InxGa1−xAs/GaAs (100) system demonstrates that the thermal effect lowers the critical layer thickness significantly on both systems, in excellent agreement with experimentally measured values. Empirical formulae of the critical layer thickness in terms of a mole fraction and temperature for these systems are provided. ©1995 American Institute of Physics.