1. Tocopherol concentrations in plasma, red blood cells (RBCs), and buccal mucosal cells were examined in newborn infants (before feeding), children (2-15 years old), and adults. Tocopherol concentrations in adults and newborn infants showed the greatest difference in plasma and the smallest difference in RBC. Buccal cell tocopherol concentrations in adults were 2.3 times higher than those in infants. The majority of newborn infants had RBC tocopherol levels below the normal limit (115 micrograms/100 ml of packed cells). Also, more than one third of buccal cell tocopherol levels determined in newborn infants were below a level of 15 ng/mg protein, which was determined as the lower limit of normal in healthy children on the basis of the testing of 97 samples. 2. After administration of a daily dose of 600 mg of RRR-alpha-tocopherol for three months to young adults, tocopherol levels in buccal mucosal cells reached a level of more than 4 times the basal level after rising throughout the 3-month period, while levels in RBC and plasma showed less than a 3-fold increase and reached a maximum within one month. Buccal cell tocopherol levels showed a poor correlation to the RBC and plasma tocopherol levels, while the tocopherol/lipid ratio was closely correlated with RBC and plasma tocopherol levels. After a single dose of 600 mg of RRR-alpha-tocopherol, RBC and plasma tocopherol concentrations reached a maximum within 24 hours, while buccal cell tocopherol did so 4 to 6 days later. 3. Very obese children and hyperlipemic obese children showed lower buccal cell tocopherol levels, accompanied by lower RBC tocopherol levels and higher plasma tocopherol levels, when compared with non-obese children and normolipemic obese children.