BACKGROUND & AIMS: Reports regarding the pro- or anti-inflammatory effects of lipid emulsion used in parenteral nutrition are conflicting. Aim was to assess the effect of different intravenous lipid emulsions on immunological function in humans. METHODS: We performed a computerized bibliographic search, searched reference lists in trial reports, hand-searched journals and contacted experts in the field. Randomized clinical trials evaluating the immunological effects of different parenteral lipid emulsions were included. Three authors independently performed data extraction, statistical processes were performed by two experts. Immunological parameters were classified by two immunologists as marker of improved or worsened immune function. A meta-analysis with standardized effect size estimation was performed for the comparison between long-chain triglycerides vs. glucose or other fat emulsions. RESULTS: Of 682 assessed studies, 120 compared the immunological effects of intravenously applied lipid emulsions. Of 30 randomized trials, 14 were included in the meta-analysis. None of the lipid regimens showed any clear effect on the evolution of the immunological status or mortality in humans. Length of hospital stay and stay in the intensive care unit could not be evaluated. CONCLUSION: We found no evidence that lipid emulsions and in particular those containing long-chain triglycerides have an unfavorable effect on immune function.