We studied the alterations in the concentrations of total cholesterol, high-density lipoprotein cholesterol, triglycerides, and apoproteins A and B in serum of 54 patients hospitalized for various reasons, who developed sepsis during their stay. Forty of these patients required intensive care, 14 did not. Another group of patients with the same underlying pathological conditions was used as a control. We found the following: Sepsis causes the concentrations of total cholesterol, high-density lipoprotein cholesterol, and apoproteins A and B in serum to decrease, whereas triglycerides increase. However, these changes are not related to the infectious agent, the underlying illness, or the clinical situation of the patients. The return of serum lipids to more normal concentrations parallels the recovery from sepsis. The positive correlation between the drastically decreased concentrations of high-density lipoprotein cholesterol and the severe hypoalbuminemia in these patients suggests a common pathway for these two abnormalities.