Physicians often express concern about the reliability of critically ill patients' preferences regarding life-sustaining treatments. We interviewed 30 Veterans Administration intensive care unit patients to determine their preferences for resuscitation, resuscitation requiring mechanical ventilation, artificial hydration and nutrition, and hospitalization for treatment of pneumonia. Patients expressed their preferences considering their current health and then two hypothetical scenarios, stroke and dementia. Follow-up interviews occurred one month later to assess preference stability. We found a diversity of opinions about life-sustaining treatments. Despite significant changes in health status and mood (p less than 0.05), treatment preferences were stable over time (kappa = .35-.70). Our results suggest that life-sustaining treatment preferences solicited during a serious illness are reliable and may be used in decision-making when a patient becomes unable to communicate or is mentally incapacitated.