Solid solubilities and optical bandgaps on a large number of pseudobinary (III‐V)‐(II‐VI) systems have been studied. Four systems, GaAs&sngbnd;ZnO, GaAs&sngbnd;CdS, InP&sngbnd;ZnO, and InP&sngbnd;CdS, were found to be completely immiscible. Five systems, GaAs&sngbnd;ZnS, GaAs&sngbnd;ZnTe, InP&sngbnd;ZnS, InP&sngbnd;ZnSe, and AlSb&sngbnd;ZnTe, exhibited partial miscibility. Only three alloy systems, GaAs&sngbnd;ZnSe, GaP&sngbnd;ZnSe, and GaP&sngbnd;ZnS, were found to form solid solutions throughout the entire system. The dependence of lattice parameter on composition for the GaAs&sngbnd;ZnSe system is sublinear, while for the GaP&sngbnd;ZnSe and GaP&sngbnd;ZnS systems, it is approximately linear. The dependence on composition of optical bandgap for the first system is sublinear, and the dependence both in the second and third systems is anomalously sublinear, with the greatest changes occurring near the II‐VI end component. Preliminary analyses of optical absorption data in all the three miscible systems indicated the existence of direct bandgap material. Preliminary doping results indicated that some GaAs&sngbnd;ZnSe and GaP&sngbnd;ZnSe compositions can be doped bothn‐ andp‐type.