The historic development of the ternary chalcopyrite CuInS2 into an efficient thin film solar cell absorber material is reviewed beginning with the preparation and analysis of crystalline and large grain polycrystalline material. The room temperature phase relations obtained by a combination of the nuclear probe method perturbed angular correlations and X-ray diffraction are presented. It is shown that despite the efforts in analysis and crystal preparation, the solar-to-electrical conversion efficiency remained generally restricted to values around 4%. Whereas a singular growth result yielding 9.7% efficiency in a photoelectro-chemical solar cell was obtained on n-type material, the subsequent successful development of thin film absorbers prepared by physical vapor deposition used p-type samples. The compositional and optoelectronic properties of these samples are described and a selection of recently achieved improvements, based on electrochemical conditioning, is presented. In the effort of elucidating the interface behavior of the {112} growth face which dominates at the polycrystalline absorber surface the preparation of epitaxial thin films have been prepared and their properties are shortly described. Aspects for implementation of this chalcopyrite in a solar technology are discussed. (C) 2004 Published by Elsevier B.V.