Diets supplemented with enzymatically produced structured lipid (SL) containing n-3 polyunsaturated fatty acids (eicosapentaenoic and docosahexaenoic) and caprylic acid or soybean oil (16.7 g/100 g) were fed to 4 to 6 week old female mice for 21 days. The effect of the diets on serum lipids (HDL-cholesterol, LDL-cholesteol. total cholesterol, triacylglycerol) and glucose concentrations were determined. The concentration of total cholesterol (49%), LDL cholesterol (35.4%) and triacylglycerol (53.2%) were significantly lowered in SL-fed group. The body weight gain in mice fed the soybean oil diet (control group) was significantly (p<0.05) greater than that in mice fed the SL diet after 21 days. The proportion of total T-cells (Thy 1.2+), T helper cells (CD4+), and T cytotoxic-suppressor cells (CD8+) in spleen were not significantly different between the two dietary groups as determined by flow cytometry.