The purpose of this presentation is to report the valence band offset assignment in Zn1-xCdxGa2Se4/ZnGa2Se4, Zn1-xHgxGa2Se4/ZnGa2Se4, Cd1-xHgxGa2Se4/CdGa2Se4, HgGa2-xInxSe4/HgGa2Se4 heterojunctions using transition metal energy level in the gap as a reference. We used the energy level of Co2+ in defect chalcopyrite solid solutions to evaluate the valence band offset. The composition dependent energy gaps E(g)(x) are presented along with E(g)Co2+ (x), i.e., energy gaps of cobalt doped solid solutions. The valence band offset is expressed as the difference in energy gap between pure and cobalt doped solid solutions.