Refractive indices ofMgx(Zn0.48Cd0.52)1−xSecompounds grown on InP substrates were systematically investigated as a function of Mg composition(x).The refractive indices with various Mg compositions were estimated from the reflectance measurements. By approximating the refractive indices by the modified single effective oscillator method, the direct band gap energyE&Ggr;=2.03+1.45x,the dispersion energyEd=24.5−15.2x,and the oscillator energyE0=5.13−1.03xwere obtained. MgZnCdSe multilayer distributed Bragg reflectors (DBRs) designed by using the refractive indices obtained in this study were fabricated by a molecular beam epitaxy. As a result, high reflectance values over 98&percent; at 595 nm were experimentally obtained for the 30 pairsMg0.1(Zn0.48Cd0.52)0.9Se/Mg0.6(Zn0.48Cd0.52)0.4SeDBR, and the reflectance spectrum agreed with the theoretical values. Furthermore, good agreements of the experimental and the theoretical maximum reflectance of the DBRs as a function of the layer pair number are obtained. From theoretical investigations of 500–600 nm wavelength range DBRs, reflectance values of 99.9&percent; are calculated for the layer pair numbers from 30 to 40. ©1997 American Institute of Physics.