We report a fast, simple high-performance liquid-chromatographic assay for serum alpha-tocopherol, with use of a reversed-phase column and tocol as internal standard. Only 200 microliter of serum is required. Isocratic elution of the n-hexane extract is done within 6 min; total analysis time is less than 1 h. Within-day precision (CV) was 2.3% for 24 samples of a normal plasma pool (mean concn, 10.1 mg/liter). Day-to-day precision (CV) was 3.2%, measured for 20 days for a specimen with a concentration of 10.8 mg/liter. Analytical recovery of alpha-tocopherol from fortified serum was 89 to 100%. The lower detection limit of alpha-tocopherol is estimated to be 0.6 mg/liter. The specificity of the procedure was verified by spectrophotometry, gas-liquid chromatography, and combined gas chromatography/mass spectrometry of an eluate collected from the column.