Preliminary predictions of the 137Cs contamination in upland lambs in west Cumbria resulting from the Windscale and Chernobyl accidents are presented. The predictions are made using the RUINS model and are tentative, particularly for the Windscale accident given the paucity of data available with which the model can be tested. For a typical scenario, whereby upland lambs are fattened on lowland pasture and slaughtered during February, 137Cs activity concentrations in the first year afeter deposition of 8000 Bq m-2 are predicted to have been in the region of 8.8 +/- 3.5 - 28.8 +/- 11.52 Bq kg-1 FW for the Windscale accident and 1.1 +/- 0.5 - 2.8 +/- 1.2 Bq kg-1 FW for the Chernobyl accident depending upon grazing pressure. If an earlier slaughter date is assumed, then the values increase for the Windscale accident to 240 +/- 96 - 290 +/- 116 Bq kg-1 FW, but there is little effect for the Chernobyl accident. For lambs fattened upon upland pasture, currently unusual, but which did occur in 1957: mean 137Cs activities in 1957/58 have been estimated to be in the range 2320 +/- 928 Bq kg-1 FW. In west Cumbria in the first year after each accident the Windscale fire is concluded to have resulted in higher 137Cs activity concentrations of upland sheep for human consumption than the Chernobyl accident. This was principally due to the timing of the accidents, but could have been exacerbated significantly by differences in farming practice. However, deposition from the Chernobyl accident was more widespread, therefore affecting a greater number of sheep.