Chemical bath-deposited (CBD) cadmium sulfide has been a component in some of the most efficient Cu(In,Ga)Se(2)-based solar cell devices. While accurate in situ measurements of the thicknesses of Vacuum-based depositions can be accomplished with quartz crystal monitors, solution-based growth rates of CdS vary greatly oil different substrates and are therefore difficult to measure. This work discusses the effectiveness of using an optical reflectance-based measurement of the growing film to determine the film's thickness. On specular molybdenum films the Measurement is accurate, while oil the tough, poorly reflecting Cu(In,Ga)Se(2) (CIGS) films, the measurement is hampered. (C) 2009 Elsevier B.V. All rights reserved.