The determination of elemental composition and thickness of single-layer and multilayer thin films by X-ray fluorescence is described. Analysis of complex single-, double- and triple-layer thin films using the fundamental parameter method shows that the inter-element and inter-layer X-ray absorptions and enhancements in a specimen have been determined properly. X-ray fluorescence results on various single-layer FeNi thin films agree with those obtained by atomic absorption spectroscopy, electron microprobe and interferometer methods. The average deviations are 0.7% in composition and 2.3% in thickness. The precision of the multilayer thin film analysis has also been evaluated and compared with analyses of single-layer films prepared under identical conditions. For triple-layer chromium, NiFe and copper films, the discrepancies are 0.25% in composition and less than or equal to 3.2% in thickness. Analysis of a double-layer FeMn/NiFe thin film with iron as a common element has also been successful with a precision comparable with those of the single- and triple-layer thin film analyses. © 1988.