The definition of an acceptable risk involves many facets most of which are outside the control of the decision maker, but they must be recognized if a proper definition is to be made. Six of the principal factors are stated and discussed. (1) nothing is absolutely safe; (2) each individual or group of individuals has his own standards by which he judges risk; (3) perceptions of risk vary with the conditions at any one time in history; (4) there must be a compensatory benefit for taking any risk; (5) societal perception of a risk may be different from the actual risk; and (6) safety is only one of the many factors that must be considered in the design of a product or service.