Soil erosion on agricultural land has become a global environmental problem and information on rates of soil loss is an important requirement both for quantifying the problem and for developing improved land management and soil conservation practices. The use of fallout137Cs measurements overcomes many of the difficulties facing traditional approaches to erosion monitoring and affords an effective means for obtaining estimates of soil redistribution rates on cultivated land. A number of empirical functions and theoretical models have been developed to establish the relationship between the change in the soil137Cs inventory relative to the local137Cs fallout input and the rate of soil redistribution. Of these approaches, physically-based mass balance models have received increasing emphasis, but their application may be hampered by their complexity and the need to specify values for a number of parameters. This paper presents a refined simplified point-based mass balance model for deriving estimates of soil redistribution rate from soil137Cs data for individual sampling points. This model incorporates a number of important factors which are included in more comprehensive mass balance models. A spatially-averaged mass balance approach is also presented. This can be used to estimate water-induced soil erosion rates at different spatial scales in situations where detailed information on within-field variation of soil redistribution rates is not needed but information on net erosion rates or sediment output from a field is required.