Bob Corbett recounts the joke about the cowboy with the arrow sticking through his chest. "It only hurts when I laugh," he quipped. It is an old story, and for doctors it is an even older problem. The problem is suffering, more narrowly defined, "pain." It is something like the weather. Everybody talks about it, but the only person who really knows what it is all about is the individual who is experiencing it. We sometimes refer to someone we dislike as "a pain in the neck." It demonstrates something of the nature of pain--often hard to diagnose and even harder to treat.