Valley floor geomorphology, sedimentology and radiocarbon dating have been used to reconstruct variations in flooding during the Holocene at six sites within the upper Severn, Teifi and Dee catchments in Wales, UK. High-magnitude palaeoflood deposits, for which ages were estimated, were identified at three floodbasin sites in the upper Severn and Teifi catchments. At the remaining sites fluvial discontinuities, indicative of episodes of increased flooding, were identified. Data from these six sites, and six additional sites studied previously, indicate that seven probably centennial length episodes of major flooding have occurred in Wales since c. 7000 cal BP. These flooding episodes occur at similar times to peaks in flood frequency within Great Britain as a whole.