Medical research that involves human subjects presents what appears to be an intractable ethical problem: patients are exposed to risks in order to create valuable knowledge. A central goal of research is to produce knowledge that is "important," "fruitful," or that will have "value." Indeed, federal regulations require that research risks be reasonable in proportion to potential benefits, and in proportion to the importance of the knowledge to be gained (45 CFR 46.111(a)(z)). Moreover, one reason that subjects participate inresearch is to produce knowledge that will benefit others.