The effects of alpha-tocopherol-nicotinate on the microdynamic parameters, membrane viscosity, and wobbling angle of phospholipid molecules of healthy human erythrocyte membranes were studied with a nanosecond time-resolved fluorometer. The incorporation of alpha-tocopherol was achieved by oral administration of alpha-tocopherol-nicotinate for one month with dosage of 400 mg/day. The increase in alpha-tocopherol concentration in erythrocytes was confirmed in two subjects. The membrane viscosity in seven healthy subjects decreased significantly from 1.015 +/- 0.137 to 0.888 +/- 0.133 mPa.s. But no changes in the wobbling angle of phospholipid molecules were observed.