Background: A new intravenous lipid emulsion (ILE) prepared from a mixture of soybean and olive oils contains only long-chain triacylglycerols, with a low proportion (20%) of polyunsaturated fatty acids and 60% monounsaturated fatty acids. Objective: The goal of this randomized, double-blind clinical trial was to assess in children the efficacy and safety of this new ILE compared with a control group receiving a soybean-oil emulsion. Design: Eighteen children received for 2 mo 24% of nonprotein energy (1.80 g.kg.d(-1)) either as the new ILE or a soybean oil-based emulsion. Assessments were performed on days -30, 0, 30, and 60 and the changes (day 60 - day 0) assessed by analysis of variance. Results: There were no significant differences in triacylglycerol, apolipoproteins A-I and B, or HDL cholesterol between the 2 groups, whereas total and LDL cholesterol were higher in the soybean oil group on day 60. The pattern of 20:4n-6 in erythrocyte membranes did not change significantly, nor did the ratio of 20:3n-9 to 20:4n-6. On day 60, 18:In-9 was significantly higher in the olive oil group, the ratio of Sigma n-6 > C-18 + 18:3n-6 to 18:2n-6 was 2.20 +/- 0.09 in the olive oil group and 1.33 +/- 0.16 in the soybean-oil group, and Sigma n-3 > C-18 was 3.83 +/- 0.30 in the olive oil group and 4.03 +/- 0.33 in the soybean-oil group. The peroxidation index was lower after the olive oil treatment. Conclusions: The olive oil-based emulsion was well tolerated, maintained a normal EFA status, and may be more suitable for prevention of lipid peroxidation than the soybean-oil-based emulsion.