Twenty-one protein-calorie depleted patients were given for one week total parenteral nutrition (TPN) including Intralipid during a sixteen months' period (September 1975 - December 1976). Before TPN, lymphocyte proliferation response to 1 microgram/ml of phytohemagglutinin (PHA) was abnormally low, while immunoglobulin levels were in the normal range. After one week of TPN, lymphocyte response to PHA was significantly improved in patients exhibiting positive nitrogen balance but remained unchanged in the others. Immunoglobulin IgA, IGG, IgM levels tended to rise in most of the patients, while IgE concentrations remained unchanged. Addition of Intralipid at various concentrations to lymphocyte cultures of both patients and normal volunteers did not effect 3H-thymidine incorporation in the lymphocytes. Similarly, in vivo infusion of Intralipid in normal subjects did not have any effect on lymphocyte performance. This study shows that: 1. effective TPN can correct some alterations in immune parameters; 2. Intralipid does not seem to have any effect on the parameters measured in the present work.