The CAncer Rehabilitation Evaluation System (CARES) (CARES Consultants, Santa Monica, CA) a rehabilitation and quality of life instrument with well-documented reliability and validity, has been shortened. This report describes the development and psychometric properties of the new instrument, the CAncer Rehabilitation Evaluation System--Short Form (CARES-SF). The data from four existing samples of cancer patients demonstrate that the CARES-SF is highly related to the CARES (r = 0.98), has excellent test-retest reliability (86% agreement), concurrent validity with related measures, and acceptable internal consistency of summary scales (alpha = 0.85 to 0.61). In a new sample of breast cancer patients evaluated at three points in time (1 month, 7 months, and 13 months after diagnosis) the instrument appears to be sensitive to change and is highly related to the Functional Living Index--Cancer (FLIC), an existing quality of life instrument. The authors conclude that the CARES-SF has excellent potential as a quality of life instrument for use in clinical trials.