A contemporary focus on outcomes assessment has provided affirmation that patient functional status is both an important outcome of medical care and an important predictor of longer term outcomes such as morbidity and/or mortality. Monitoring functional status among end-stage renal disease (ESRD) patients is particularly critical because the cycle of physical deconditioning experienced by renal patients is both insidious and malignant. Over the past several years, patient self-report instruments have been used with increasing frequency to assess functioning. Among ESRD patients, such self-reports have reliably predicted mortality and some morbidity. Additionally, renal patients' self-reported functioning is also correlated with the results of several commonly performed laboratory tests. Based on these findings, measures of self-reported functional status might be considered a practical adjunct to regular patient assessments. They could be routinely used for purposes that might include: identifying the particular areas of functioning and well-being that need improvement; screening for subtle changes in health status; establishing physical status baselines; and corroborating the effectiveness of physical activity interventions. Overall, ESRD patients' self-report of their functioning appears to secure, synthesize, and standardize data about patient health status that is unavailable through any other mechanism. Such information may be essential to medicine's primary missions of promoting health and preserving life.