Practicalities of lipids: ICU patient, autoimmune disease, and vascular disease. Although the use of lipids should be individualized, certain generalizations are appropriate. 1. Lipid infusion should be limited in the fulminately septic patient to 10% of total calories in an effort to reduce immunosuppression. 2. The stressed, nonseptic patient with difficulties in ventilator weaning or TPN-induced hepatic dysfunction may reap benefit from a reduction in dextrose calories and the provision of daily lipids. 3. Patients with severe autoimmune disease have had mild amelioration of symptoms with PUFA supplementation. The relative benefits of omega-6 vs omega-3 continue to be examined. 4. Dietary immunomodulation in transplant and burns remains an area of active investigation. 5. Patients with fat-free TPN show transient declines in serum lipids. The development of a "fat-solubilizer" remains in the experimental realm. 6. The provision of fish oil, high in W-3 EPA, has shown promise in atherosclerosis and immunomodulation. The changes in the relative amounts of each prostaglandin class depend on precursor prevalence. 