The method of diffuse laser light scattering (LLS) has been tested for process monitoring of simultaneous and sequential chalcopyrite film formation. Characteristic LLS features are observed which can be assigned to morphological and optoelectronic film modifications. The surface roughness development as a function of time of CuInS2 and CuInSe2 epilayers grown on Si(111) substrates is monitored. It is found that the critical thickness of a smooth surface without islands depends on the film composition (Cu/(Cu+In) ratio). LLS transients for sequential film formation depict a series of characteristic features which are connected with, e.g., precursor transformation, surfacial sulfurization, and secondary phase transformation.