ZnSe/CuGaSe2 heterojunctions were prepared by growing CuGaSe2 absorber layers onto the (110) surface of ZnSe single crystals by flash evaporation, physical vapor deposition, chemical vapor deposition and metal-organic vapor phase epitaxy. The morphology of the absorber layers was studied by scanning electron microscopy. Elemental distribution in the thin films investigated and along the heterojunction cross-section was characterized using energy-dispersive X-ray analysis. All heterojunctions prepared show high open-circuit voltages of 0.85-1.12 V, which slightly depend on the preparation method. Currents through the ZnSe/CuGaSe2 heterojunctions are limited by the presence of a high-resistivity (p similar to 10(8)-10(9) Omega cm) i-ZnSe layer at the interface, which is highly compensated by Cu impurities.