There is a growing recognition that clinical research needs to define and focus on the outcomes of medical care which are important to patients. The outcomes important to patients have been coined "patient-centered" outcomes. In the past, clinical research in critical care medicine has tended to focus on survival and physiologic impairment, and not as much on outcomes such as functional status and quality of life. While survival and physiologic impairment are the appropriate outcomes in some settings, we also need to address important questions about the effect of critical care medicine on other outcomes. The goals of this article are to describe the patient-centered outcomes of critical care research, to identify important issues and pitfalls in measuring these outcomes, and to identify the situations in which these outcomes may be more or less important. The outcomes addressed include: mortality, patient-assessed outcomes (quality of life, functional status, and health status), physiologic parameters, process-of-care measures, and quality of death.