Protein-calorie malnutrition is common in maintenance dialysis patients. Malnutrition is mild to moderate in approximately 33% of maintenance dialysis patients and severe in approximately 6% to 8%. There are many causes of protein-calorie malnutrition in maintenance dialysis patients; the three major causes are probably low nutrient intakes, intercurrent or underlying illnesses, and the dialysis procedure itself. Malnutrition is a major risk factor for mortality in maintenance dialysis patients. This has been shown most clearly for serum albumin, which is the nutritional parameter that has been most heavily studied. Low dietary of protein or other nutrients and protein-calorie malnutrition revealed by the results of different chemistry analyses are also directly correlated with mortality rates. These data do not prove that poor nutritional intake or malnutrition is a cause of the high morbidity and mortality in maintenance dialysis patients, and randomized, prospective controlled clinical trials are necessary to answer this question. However, the data are consistent with the thesis that malnutrition or inadequate nutrient intake do contribute to high morbidity and mortality in these patients. Although it is possible that increasing the dose of dialysis (eg, Kt/V) will lead to increased appetite and nutrient intake, experience suggests that raising the dose of dialysis, by itself, will not optimize nutritional intake in these individuals. To achieve satisfactory nutritional intake and healthy nutritional status, other interventions will need to be developed.