Background: The bioelectrical phase angle has shown predictive potential in various diseases, but general cutoffs are lacking in the clinical setting. Objectives: This study evaluated the prognostic value of the fifth percentile of sex-, age-, and body mass index-stratified phase angle reference values in patients with cancer with respect to nutritional and functional status, quality of life, and 6-mo mortality. In a second step, we also studied the effect of the standardized phase angle (with a z score to determine individual deviations from the population average) on these variables. Design: A total of 399 patients with cancer were studied. Phase angle was obtained with bioelectrical impedance analysis; muscle function was assessed by handgrip strength and peak expiratory flow. Quality of life was determined by the European Organization for Research and Treatment of Cancer questionnaire. Nutritional status was assessed by using Subjective Global Assessment. Survival of patients was documented after 6 mo. Results: Patients with a phase angle of less than the fifth reference percentile had significantly lower nutritional and functional status, impaired quality of life (P , 0.0001), and increased mortality (P , 0.001). The standardized phase angle emerged as a significant predictor for malnutrition and impaired functional status in generalized linear model regression analyses. It was also a stronger indicator of 6-mo survival than were malnutrition and disease severity in the Cox regression model (P , 0.0001) and according to the receiver operating characteristic curve. Conclusions: The standardized phase angle is an independent predictor for impaired nutritional and functional status and survival. The fifth phase angle reference percentile is a simple and prognostically relevant cutoff for detection of patients with cancer at risk for these factors.Am J Clin Nutr 2010;92:612-9.