This report describes a patient in whom a severe vitamin E deficiency developed secondary to an intestinal malabsorptive disorder. In vivo and in vitro impairment of T-cell function, as well as a polyneuropathy, were observed in conjunction with this vitamin deficiency. Repletion of the vitamin deficiency was associated with marked improvement in the T-cell functions and modest improvement in the neuropathy. Observations in this patient suggest that severe vitamin E deficiency in humans may impair T-cell activity and that correction of the deficient state may reverse these T-cell abnormalities. Further studies will need to be performed to confirm these findings.