Previous studies have shown that postprandial triglyceride-rich lipoproteins (TRLs) are enriched with apolipoprotein-C-I (apoC-I) in healthy individuals with increased intima-media thickness and in patients with coronary artery disease. The purpose of the present study was to determine apoC-I in TRL in persons with carotid atherosclerosis and its relation to plaque area. A population-based case (n = 42)-control (n = 39) study was conducted in persons with carotid atherosclerosis, assessed by B-mode ultrasound, and healthy controls. VLDL (Sf 20-400) was isolated in the fasting state and 4 h after ingestion of a standard fat meal. In the fasting state, persons with carotid atherosclerosis had increased number of apoC-I per VLDL-particle compared to persons without carotid atherosclerosis (8.6 +/- 5.4 vs. 6.3 +/- 4.2, P = 0.018). Total plaque area increased linearly (P = 0.017) across tertiles of apoC-I per VLDL-particle. In the postprandial state, a similar increase in the number of apoC-I per VLDL-particle occurred in both cases and controls (P < 0.001), but no significant difference was observed between groups. The number of apoC-I per VLDL-particle in the fasting state was accompanied by delayed clearance of TRL in the postprandial state, and associated with cholesterol enrichment of the VLDL-particles. Our findings support the concept that the number of apoC-I per VLDL-particle may be of importance for initiation and progression of atherosclerosis.