Potential exposures are not normally expected to occur, but they can be anticipated, and the probability of their occurrence can be forecast. Early ICRP thoughts about this concept were developed in considerations about final disposal of long-lived radioactive waste, and about major accidents such as nuclear disasters. ICRP has now examined a third situation: accidents affecting one or a few persons only (but sometimes with severe consequences for those affected). Protection against such potential exposures starts with a structured analysis of scenarios. Given probabilities derived from such analyses, the expected detriment from potential exposures can be computed. This risk can be compared to a risk constraint, which need not be particularly complicated.