Plasma tocopherol, plasma total lipid levels and tocopherol-lipid ratio were measured every 6 h during 48 h in 12 critically ill patients and compared with those of a control group. The patients were divided into two groups. Group I comprised 6 critically ill patients with ARDS and group II comprised 6 severely ill patients without ARDS. The means for all observations of plasma tocopherol, total lipid levels and tocopherol-lipid ratio in groups I and II were significantly depressed relative to a control group (p less than 0.0001). The difference in the average tocopherol-lipid ratio between the three groups (p less than 0.0001) and between the groups I and II was statistically significant (p less than 0.0001). Our results indicated: (1) a decrease of vitamin E concentrations in the critically ill patients, particularly in ARDS patients; (2) the importance of the relationship between plasma tocopherol and plasma lipids levels in evaluating the deficiency in vitamin E which was evident in ARDS patients.