The increasing complexity of modern hospital care and the decisions that must be made were the reasons we began our research on the Acute Physiology, Age and Chronic Health Evaluation (APACHE) project. As a clinician in an intensive care unit (ICU), I felt very uncomfortable making the sorts of decisions that are common today without any source of information or any reference points. These decisions are not avoidable, they are not discretionary, and they are going to become more frequent in the future because we are treating people at later stages of disease.