Epidemiologic studies suggest that elevated postprandial triglycerides (ppTG) are associated with future cardiovascular events. Monocyte activation plays an important role in vascular diseases. Omega-3 fatty acids (n3-FA) lower fasting TG levels. The effects of n3-FA on ppTG and the role of ppTG for monocyte activation are insufficiently understood.23 healthy volunteers and 30 non-diabetic patients with documented coronary artery disease were subjected to an oral TG tolerance test (OTTT) consisting of 80 g cream fat or to water as control (H(2)O). Patients were treated with 4 g n3-FA/day or placebo for 3 weeks in a randomized, placebo-controlled, double-blind, crossover study. Relative postprandial TG increase reached its maximum 4 h after fat intake (185.1 ± 10.9% of baseline). n3-FA reduced fasting TG from 137.1 ± 12.9 to 112.2 ± 8.6 mg/dl (p 0.05), and maximum ppTG concentrations from 243.6 ± 24.6 to 205.8 ± 17.1 mg/dl (p 0.05), while relative TG increase (192.8 ± 12.7%) was comparable to placebo. Relative monocytopenia and neutrophilia were detected following fat intake, which was unaffected by n3-FA and also detectable in the H(2)O group. Serum chemotactic cytokine (MCP1 and fractalkine) concentrations and monocyte migration were not affected by fat intake or n3-FA. Monocyte activation markers CD11b and CD14, monocyte subpopulations CD16(+)CD14(high) and CD16(+)CD14(low), sICAM serum levels and markers of oxidative stress remained unchanged by fat intake or n3-FA.The postprandial TG increase does not stimulate monocytes beyond their circadian activation patterns. n3-FA reduce fasting TG and the postprandial TG increase. n3-FA may therefore allow to prospectively study whether selected patients benefit from TG-lowering independent of LDL- and HDL-cholesterol.