It is argued that since risk contains an element of human perception about the desirability of outcomes, it cannot be predicted by scientific methods. The term chance is used to distinguish between risk and the calculable outcomes of events. It is argued that for many technological innovations the possible outcomes are not calculable because there is an insufficient knowledge base. In this case, the uncertainty of predictions must be explicitly acknowledged. In the particular case of food, it must be recognised that technology touches lives in a directly personal way. Attitudes to food technology will not, therefore, be formed on the basis of technical assessments and many other factors will need to be taken in to account when acceptable risk is assessed.