AbstractA low dilution fusion (LDF) technique using a 2:1 flux‐to‐sample ratio has been developed for the accurate determination of major, minor and trace elements in rock samples by wavelength‐dispersive x‐ray fluorescence spectrometry (XRFS). The choice of flux, oxidant and the dilution ratio and the application to trace element analysis are discussed. The elimination of particle size effects in the homogeneous glass fusion discs is a major advantage over the use of powder pellets, especially for the determination of elements such as Ba, Cr and the REEs. The fusion technique ensures complete loss of volatiles from the rock samples and provides an accurate estimation of loss on fusion values. The oxidation and retention of sulphur in the discs were also investigated. Instrumental conditions, including corrections for spectral line interferences, are reported for 20 trace elements. The average relative error for the trace elements commonly analysed in rock samples was less than 5% and there was a decrease in sensitivity by about a factor of 2 compared with XRFS determinations on powder pellets. The LDF method has been used for the analysis of geological samples of widely varying and unusual composition, such as lamproites and kimberlites, but is also suitable as a general‐purpose sample preparation