Essential fatty acid (FA) deficiency, which may accompany protein-energy malnutrition (PEM), has been associated with impaired inflammatory reactions. We evaluated this relationship by analysing FA profiles and delayed cutaneous hypersensitivity in 20 malnourished elderly non-cancer patients and in 20 age-matched control patients. As indicated by serum cholesterol and serum triglycerides, the lipid levels were decreased by about one-third in the subjects with PEM. In comparison with the controls, there was a reduction in the omega 3 FA (e.g. eicosapentanoate) in total serum lipids (mg l-1) and serum phospholipids (%) of 40% and 47%, respectively. Reductions in serum omega 6 FA (e.g. linoleate and arachidonate) levels corresponded to the drop in total FA concentrations (30%). The cutaneous hypersensitivity was impaired in 14 of the malnourished patients. The magnitude of the skin reaction was positively correlated (P < 0.05) to the concentrations of eicosapentanoate in serum lipids and serum phospholipids, as well as to the linoleate concentration in total serum lipids. Six of the malnourished patients took part in a nutritional intervention programme for 3 months. In parallel with an improvement in the nutritional status there was a 35% increase (P < 0.05) in the total omega 3 FA serum concentration. Negative skin tests became positive and the median skin induration enlarged threefold (P < 0.05). Thus, deficiency of omega 3 FA might be one factor contributing to cutaneous anergy in elderly malnourished patients.