In this work the selenization reactions and reaction paths in CuIn(x)Ga(1-x)Se(2) thin films prepared by sputtering and post-selenization process are investigated. The in-situ electrical resistance measurement technique is applied to monitor all the selenization reactions. The crystal structure is determined by X-ray diffraction (XRD) measurement. From the analysis of resistance-temperature curves and the XRD patterns, the phase evolutions of various crystalline and selenization reaction paths have been obtained. From these measurements, the reaction mechanisms and kinetics in the CuInGa-Se system are further understood. (C) 2010 Elsevier B.V. All rights reserved.