Thin films and crystals of chalcopyrite semiconductors of the type CuBCh₂ (B=In, Ga; Ch=S, Se) are investigated for optoelectronic devices such as solar cells. Due to their large optical absorption coefficient, light is mainly absorbed in a near surface region. This makes chalcopyrite based devices highly sensitive to surface and interface modifications. In this paper we review recent work on electronic and structural properties of chalcopyrite surfaces. Formation and preparation of clean surfaces under UHV conditions are critically discussed. Clean surfaces of thin films and crystals may show pronounced stoichiometry deviations and phase segregations which can be explained by phase relations in the ternary phase diagram. These stoichiometry deviations an induce a conversion of the conduction type at the surface, i.e. an intrinsic band bending or buried junction. Adsorption of inorganic and organic species has been investigated for the modification of electronic surface properties. We will consider the formation of heterocontacts and their electronic and structural interface properties. The experimental and theoretical determination of the band line-up to most prominent heteropartners is reviewed. The implications of the band line-up for heterojunction solar cells will be discussed.