A general theory is presented for small thermoelastic deformations in a body which has already been subjected to an elastic deformation and which was initially aeolotropic. Two special cases are examined in detail. The first is concerned with small thermoelastic deformations in a body which is under initial stress, the state of initial stress not necessarily being obtained by elastic deformation from some other unstressed state. The propagation of plane waves under isothermal or isentropic conditions in such a body is considered when the initial stress is homogeneous. The second special case of the general theory arises when the initial deformation is small and is obtained elastically from an unstressed state of the body. This theory is used to study the torsion of an initially stretched rhombic crystal and wave propagation in homogeneously stressed bodies.