Abstract: Major and trace element data are presented for the basic, intermediate, and acid rocks of the Beinn Chaisgidle Centre of the Tertiary igneous complex on the Isle of Mull. The variation in the bulk chemical composition, the iron enrichment trend in the clinopyroxenes, the systematic decrease in concentrations of the transition metal cations, and the increase in the incompatible elements suggest that the magma from which these rocks formed underwent crystal fractionation. The rocks show a coherence of rare earth element patterns for all the rocks in the sequence, and there is a progressive increase in negative Eu anomaly with increasing silica content.