I HAVE shown that the average compositions of granites in the Variscan, Caledonian and Alpine orogenic belts differ, and have attributed their differences to formation by partial melting under different geothermal gradients1. A geochemical examination of the granites in the Caledonian orogenic belt suggested that regional variation within the orogenic belt might also be attributable to variations in the geothermal gradient2 but a preliminary examination of the northern part of the Variscan orogenic belt did not reveal any similar pattern3. I have now extended the study to the Variscan granites in the whole of western Europe; these granites do display a regional variation which can be correlated with known geothermal gradients.