The growth temperature dependence of strain in ZnSe epilayers on (100) GaAs substrates was investigated. The strain effect was confirmed using high-resolution X-ray diffraction, Raman scattering and photoluminescence. With the increasing growth temperature, the lattice constant decreased and the Raman frequency red-shifted. Also, the near band-edge emission peak energy decreased and the energy difference between the heavy hole- and the light hole-free exciton peak increased a little. This is well explained by the thermal tensile strain remaining in the epilayer. (C) 2002 Elsevier Science B.V. All rights reserved.