This paper describes the results of predicting the reliability of a circuit at different radiation levels. The conditional mean and variance of circuit output and the conditional reliability are predicted using Sceptre and test data on components exposed to different levels of radiation. These predictions are compared with the results of tests of the circuit. The difference between predictions and tests are examined and explained. The conclusions suggest a minor modification of the proposed method. We also suggest that this method of computer-aided reliability prediction can be a valuable design aid. This is especially true when there is a significant effect due to environmental variation, such as the effect of radiation on semiconductors.