Sandstone‐filled channels occur widely in the Upper Carboniferous (Westphalian) rocks of South Wales. Subsurface and outcrop studies of channels and associated structures in three formations within the Westphalian sequence reveal significant regional variations in orientation, transverse profile, geometry and lithology of fill. The pattern of channel‐orientation in each formation is consistent with the system of palaeocurrents derived from independent studies of cross‐bedding and indicates that in the lowest Westphalian (Basal Coal Measures) derivation was principally from the north and east, with intermittent supply from the south, whereas in the Upper Westphalian material was derived mainly from the south and east but with substantial contributions from the north.Formation of the channels is ascribed to fluvial erosion and filling. The mutually consistent regional variations in channel‐parameters are compared with the conspic‐ uous changes in lithofacies and interpreted as indicating diRerences in Auviohydraulic locale within the original basin of sedi