The plasma and red blood cell (RBC) levels of alpha-tocopherol in rats were determined in association with hemolysis induced by dialuric acid for a 7-week period of tocopherol deprivation following a 2-week period on tocopherol-containing diet. The patterns of decreases in plasma and RBC levels during the 7-week period were similar, differing in one respect. The RBC levels were characterized by a prompt decrease to non-detectable levels in the 4th week, while at that time a plasma level of 100 microgram/dl, albeit low, was maintained during the subsequent two weeks. Consequently, tocopherol ratios of RBC to plasma lowered throughout the experimental course. As for the relationship between these levels and hemolysis values, non-hemolysis was recorded in animals whose minimum RBC and plasma levels were 40 microgram/dl packed cell and 180 microgram/dl, respectively. This experiment showed that the plasma tocopherol level which has traditionally been accepted as the only index of hemolysis values does not always reflect them, and that in animals with hemolysis, only RBC tocopherol levels were found to reflect hemolysis values.