The effects of dietary supplementation with a combination of conjugated linoleic acid and n-3 polyunsaturated fatty acids (CLA/n-3 LC-PUFA) on fasting and postprandial plasma lipids were investigated in lean and obese young and older healthy men. Lean (BMI 20-26 kg/m2) and obese (BMI 29-35 kg/m2), young (20-37y) and older (50-65y) men consumed 3g/d of a 50:50 isomeric blend of CLA (700mg/g CLA/g) (consisting of cis-9, trans-11: trans-10, cis-12 CLA) and 3g of n-3 marine LC-PUFA (300mg/g EPA and 210mg/g DHA) or 6g of control fat (800mg/g Palm oil and 200mg/g Soya bean oil) for 12-wk period. The study was double blinded, placebo-controlled with a randomized cross-over design. Fasting plasma lipids and postprandial responses 4h after a high fat meal were investigated after supplementation. Fasting plasma LDL-cholesterol increased (13%) whereas NEFA concentrations decreased (41%) significantly after 12-wk treatment with CLA/n-3 LC-PUFA compared to control in older obese and lean subjects, respectively. The difference in the postprandial increase in total plasma cholesterol and triglycerides before and after each supplementation was significantly lower after treatment with CLA/n-3 LC-PUFA in young obese subjects compared to control (8% and 99% decreases, respectively). Significant impairment of postprandial plasma NEFA levels was also observed in young lean subjects. However the postprandial increase in total cholesterol was significantly higher after 12 wk treatment with CLA/n-3 LC-PUFA compared to control in older obese subjects. These results suggest that supplementation with a combination of CLA and n-3 LC-PUFA may have detrimental effects on plasma lipids in older obese men.