ABSTRACTThe caesium-137 technique has been used to derive hitherto unavailable information concerning erosion rates on gully slopes in a yuan area of the Loess Plateau in Gansu Province, China. The patterns shown by the caesium- 137 inventories were used to interpret the dominant erosion processes operating on cultivated and uncultivated land. These patterns demonstrate the importance of tillage redistribution and water erosion on cultivated terraces and suggest that both wind and water erosion processes operate on grassland areas. Rates of erosion derived from the caesium-137 inventories for the sites on uncultivated land indicate that the estimate of 61 km-2year-1provided by the local soil conservation station may be a serious underestimate, although the data do confirm the importance of full vegetation cover in controlling erosion. The erosion rates derived for terraced cultivated sites are in line with published estimates. Two terrace types were examined and these were characterized by widely divergent net erosion rates, indicating that narrow-strip terraces cultivated parallel to the contour should be used where possible, because these offer a clear soil conservation benefit.