Abstract: Six hundred and forty four gamma-ray spectrometer assays of U and Th obtained within the late Caledonian Galway Granite western Ireland are presented. The data cover the range of granodiorites, adamellites and leucogranites (Murvey Granite) present in the batholith. There is an overall increase in U and Th abundances with petrological evolution. The broad scatter of values that characterizes the Murvey Granite reflects the geographically separate occurrences of this leucogranite. Rubidium and strontium data imply varying degrees of fractionation among these separate Murvey Granite occurrences. Y and HREE are notably enriched in the Murvey granite at Costelloe which also contains the highest Th levels amongst the leucogranites. Thorite, uraninite, monazite and Y-zircon are present in this leucogranite and are responsible for the observed enrichments in U, Th, Y and HREE.