Clay mineral associations of Palaeocene and Eocene age, with special attention to the late Palaeocene thermal maximum, have been examined in ten sections from the Tethys (Egypt, Israel, Tunisia, Spain and Kazakhstan) and Atlantic (England). A widespread abundance of kaolinite in marine sediments at all locations suggests a warm and humid climate with high rainfall in the Tethys region during the early Palaeocene. In the coastal basins along the southern margin (Israel and southern Tunisia), kaolinite disappears gradually giving way to palygorskite and sepiolite, suggesting the progressive development of arid climatic conditions in this part of the Tethys from the late Palaeocene to the early Eocene. Remarkably, kaolinite increases strongly throughout most of the Tethys during the late Palaeocene thermal maximum (LPTM) reflecting an episode of humidity and warmth and coincident with a global maximum warmth of seawaters inferred from oxygen isotopic data.