Long chain fatty acid fractionation has become a valuable tool in the management of patients maintained on total parenteral nutrition. While many clinicians prefer to use absolute concentrations to monitor a patient's fatty acid status, reference ranges are not available. Previous reference range studies reported values in terms of percentages only and calculated ranges parametrically. However, due to the non-Gaussian distributions of some serum fatty acids, it is necessary to calculate reference ranges non-parametrically. Serum from blood donors (n = 130) were collected and analyzed for total fatty acids by gas-liquid chromatography. Results for each of the fatty acids were calculated both as a concentration and as a percentage of the total fatty acids measured.