The production of thin films of CuInS2 by the reactive annealing process in H2S atmosphere leads to the incorporation of hydrogen. Hydrogen concentrations of up to 5 X 10(20) cm(-3) were measured by means of a nuclear reaction analysis method. No negative influence on the electrical properties of the films containing hydrogen was observed. Instead, hydrogen, when incorporated in situ, seems to help to passivate electrically active lattice defects.