Biochemical indicators of ascorbic acid (AA) status were studied in eleven young adult males fed the same AA deficient diet for 14 wk in a live-in metabolic unit. Supplements of AA were added to the diet to give AA-intake periods of 65 mg/d (2 wk), 5 mg/d (4 wk), 605 mg/d (3 wk), 5 mg/d (4 wk), 605 mg/d (4 d), and 65 mg/d (3 d). Blood plasma, erythrocyte, and leukocyte AA levels all reflected AA intake, however, plasma AA showed less variability than red cell AA levels and was considerably easier to determine than leukocyte AA. Plasma AA values less than 0.40 mg/dL (23 mumol/L) reflected marginal AA status. The daily AA intake calculated to maintain plasma AA levels of at least 0.4 mg/dL (23 mumol/L) in healthy young men was 41 mg. The average AA intake estimated to maximize the total body pool was 138 mg/d. Urine and salivary AA levels were not useful indicators of AA status because urinary AA levels did not discriminate well between adequate and deficient AA intakes and salivary AA levels did not consistently reflect AA intake.