Essential amino acid (EAA), vitamin and mineral abnormalities are found in patients with chronic renal failure (CRF). We considered altered dietary restriction to be one of many factors that can promote these abnormalities. We determined the EAA, vitamin and mineral content of low-protein diets and vitamins and minerals in the blood of outpatient populations with various degrees of CRF (serum creatinine 3.6-6.8mg/dl). The results obtained were as follows: 1. 20g-protein/day diet can provide an adequate amount of EAA. 2. Low protein diets (30g protein/day diets) were inadequate in vitamins A, B1, B2 and B6. Vitamins A, B1, B2 and B6 in these diets were 70-80%, 40-50%, 30-35% and 20-25% of the minimum daily requirements, respectively. 3. Low protein diets (30g protein/day diets) were inadequate in Ca, Fe and Zn. The Ca and Fe contents of these diets were 30% and 50% of the minimum daily requirements, respectively. The Zn content of a diet rich in vegetable protein, although low in protein, overall (vegetable: animal = 2:1), was about 55% of the minimum daily requirement. 4. About 21.4% of the CRF patients had low levels of plasma vitamins B1. About 28.6% and 33.3% of the CRF patients had low levels of plasma vitamins B2 and B6, respectively. Plasma folic acid levels were not inadequate in these patients. 5. About 28.6%, 50% and 35.7% of the CRF patients had low levels of plasma Ca, Fe and Zn, respectively. In conclusion, it seems that supplementation of vitamins B1, B2, B6, Ca, Fe and Zn should be considered for protein-restricted CRF patients.