The dielectric function and layer thicknesses of thin metal films are simultaneously determined by combined in situ spectroscopic ellipsometric (SE) transmission and transmission intensity M measurements. Adding the transmission intensity data to the SE data alleviates the difficulty of correlation between thickness and optical constants of very thin absorbing films. The SE + T data are acquired by a rotating compensator ellipsometer (RCE), using only the AC signal components. Experimental results from the deposition of Al, Co, Mo, and Ti thin films on fused silica substrates are presented. The growing films were analyzed using the real-time acquired data. The dielectric function of Al changed most dramatically as a function of film thickness, while the Ti dielectric function exhibited the least changes. (C) 2003 Elsevier B.V. All rights reserved.