Measurements of bank erosion on rivers in Devon over a 2½ year period produced mean rates ranging from 0.08 to 1.18 metres per year and a maximum rate of 2.58 metres per year. These values are compared with rates derived from maps for various time periods between 1840 and 1975. The map rates are generally lower than the field rates and the question of whether this difference is due to the method of measurement, the magnitude-frequency of events, a change in discharge conditions or the inherent variation in channel activity is discussed. Published data on bank erosion rates are reviewed and the Devon rates are found to coincide with the worldwide distribution. An analysis of factors likely to influence the spatial distribution of erosion rates reveals a square-root relationship to catchment area and the importance of bank material. Implications of the measured rates for development of flood plains are examined.