Home parenteral nutrition (HPN), initiated in patients with severe malabsorption or decreased oral intake, may exhaust stores of essential fatty acids and cause clinical manifestations, mainly dermatitis. Plasma fatty acid profiles were measured by gas-liquid chromatography in 37 healthy control subjects and 56 patients receiving HPN. The concentration (% by wt of total fatty acids) of 18:2n-6 was 22.8% and 11.4% (P < 0.001), whereas 18:3n-3 was 0.2% and 0.1% (P < 0.01) in control subjects and patients, respectively. Reduced small bowel length was associated with aggravated biochemical signs of essential fatty acid deficiency (EFAD). The effect of parenteral lipid on plasma phospholipids was evaluated in subgroups of patients. In patients with > 200 cm of remaining small intestine, those receiving parenteral lipids had only minor changes in the fatty acids of plasma phospholipids compared with patients not receiving parenteral lipids. In patients with < 100 cm of remaining small intestine, those receiving parenteral lipids had increased concentrations of total n-6 fatty acids; however, these did not reach the concentrations in control subjects. No differences were seen in n-3 fatty acids. Twenty-five of the 56 patients receiving HPN reported skin problems. No differences were found in plasma phospholipid fatty acids, Holman index, or the supply of parenteral lipids between patients with and without skin problems. Patients receiving HPN had biochemical signs of EFAD. Parenteral lipids did not increase the concentration of essential fatty acids to values comparable with those of control subjects, but 500 mL 20% Intralipid once a week was sufficient to prevent an increase in the Holman index above 0.2.