Summary Lipid emulsions used in parenteral nutrition are an essential factor of artificial nutrition in intensive care. When given according to the guidelines, they are effective on the nutritional point of view and metabolically well tolerated. Soon after being available on the market, the first generation emulsions, made from soybean oil, were thought to have a noxious effect on the immune system, especially when given in great amounts. Their high content in essential fatty acids is the main factor that causes the adverse effects of these emulsions, as they interfere with the eicosanoids metabolism and modify the cytokines production, especially in the critically ill patient. In order to optimize both the efficacy and tolerance of parenteral nutrition, new lipid emulsions gradually appeared, made from medium-chain fatty acids, structured lipids, olive oil or fish oil. In many fields, research and animal testing have shown the potential benefits of these emulsions. Clinically, results are only partial, but some interesting data are available regarding anti-inflammatory or immunomodulation effects of fish oil-enriched emulsion in sepsis, ARDS or major surgery. So far, there have not been sufficient clinical studies to evaluate the use of these new emulsions made of different oils. Even though the design of these new generation emulsions is based on strong theories and experimentations, further clinical investigations are needed to find whether they can bring a new tool in the daily clinical practice, by regulating the inflammatory reaction in the critically ill patient.