Changes in the fatty acid pattern of plasma lipid in four different groups of polytraumatized patients were investigated. All of the patients received amino acid solutions containing 0.24 gN/day/kg body weight and 30 kal/day/kg body weight (BW). In group 1, all calories were administered as carbohydrates (glucose and fructose). In group 2, 30 to 40% of the calories were provided as a fat emulsion. When compared to the control group, a reduction in the essential fatty acid concentration in the phospholipid fraction was detected in both groups during the early post-traumatic period. In group 1, a continuous decline was observed during the remainder of the trial period. In group 2, however, the concentration of essential fatty acids remained constant after the initial decline and increased slightly from the 7th day on. In the second part of the investigation, the effect of human growth hormone (HGH) administration on the fatty acid pattern was evaluated. Group 3 and 4 received intravenous feedings identical to the patients in group 2; in group 4, however, 10 mg of HGH per day were added to the infusion. The results of this study confirm the hypothesis that supplemental infusion of a fat emulsion prevents a continuous reduction of essential fatty acids in plasma lipids. An effect of 10 mg/day of HGH on essential fatty acid concentration or composition, however, could not be observed. There were no detectable differences in the percentage of essential fatty acids between those patients receiving and those not receiving HGH.