Despite the advocacy for subjective nutritional assessments, clinicians need laboratory support in their nutrition care armamentarium, first, to identify existing or developing malnutrition and, second, to monitor nutritional therapy. Visceral proteins and immune function continue to be essential, but newer means of assessing nutritional status, especially body composition, are on the horizon. Further, prognostic indicators through data analysis and computer-assisted interpretation of results may lead to more effective uses of the laboratory.