Reviews 2 Instrumentation 2.1 General instrumentation and excitation sources 2.2 Detectors 3 Spectrum evaluation, matrix correction and calibration procedures 3.1 Spectrum evaluation 3.2 Matrix correction and calibration procedures 4 X-ray optics 5 Synchrotron radiation 6 Total reflection X-ray fluorescence spectrometry (TXRF) 7 Portable and mobile XRF 8 On-line XRF 9 Applications 9.1 Sample preparation 9.2 Preconcentration techniques 9.3 Geological 9.4 Environmental 9.5 Archaeological and forensic 9.6 Industrial 9.7 Clinical and biological 9.8 Thin films 9.9 Chemical state analysis and speciationThis annual review of X-ray fluorescence covers developments over the period 2000-2001 in instrumentation and detectors, matrix correction and spectrum analysis software, X-ray optics and microfluorescence, synchrotron XRF, TXRF, portable XRF and on-line applications as assessed from the published literature. The review also covers a survey of applications, including sample preparation, geological, environmental, archaeological, forensic, biological, clinical, thin films, chemical state and speciation studies. During the current review period, publications have demonstrated the development of sub-100 nm X-ray beams for SR microprobe analysis together with the wider use of WD spectrometers in this application. There is evidence of an extension of the application of XRF as a reference technique, with XRF increasingly being used in modern laboratories in place of older wet-chemical methods, and computer-modelling studies continue to be popular in extending the understanding of various XRF phenomena. Some interesting work has been undertaken in the measurement of radiative Auger effects using high-resolution WDXRF instruments. However, the potential for future developments in XRF is illustrated by research into ultra-high resolution microcalorimeter detector devices, which are still at the experimental stage and have not yet progressed to the status of useful practical devices.