Eating potato salad left out in the sun, flying a kite in a rainstorm, sticking a fork in a light socket--we don't need an actuarial table to know that these and many other actions are downright life-threatening. Most of us grow up learning these basic lessons and think of them as common sense, not as a measure of risk. But what about having a heart attack? Contracting a fatal disease? Experiencing unusual side effects from medicine? These risks aren't so obvious. But in each situation, information is available that can identify the chances of any one of us experiencing a stroke or food poisoning. In fact, conclusions about the incidence and potential health risks are key in the daily business decisions of healthcare. Just knowing the gambles, however, is not what risk in healthcare is all about. Instead, it is about the potential costs of those risks to health planners footing the bill.