We have investigated compositional plane of a wide band gap solid solution semiconductor Ca1-xCdxSe1-ySy (x <= 0.32) using powder synthesis under thermal equilibrium condition. The solubility limit at 1273 K varies with respect to the Se concentration y, taking a minimum Cd solubility limit of 0.12 at y = 0.8 and a maximum limit of 0.32 at y = 1.0. It is found that the system can be lattice-matched to GaAs and InP under covering the energy band gap of ultraviolet-visible region. These results allow to design optoelectronic devices adopting the Ca1-xCdxSe1-ySy system. (c) 2006 Elsevier B.V. All rights reserved.