Abstract Body: Aim: The plasma unesterified-cholesterol(FC) ratio increases the risk of atherosclerotic cardiovascular disease; however, the underlying mechanisms are not fully elucidated. Therefore, we compared the characteristics of plasma cholesterol in patients with stable ischemic heart disease and in Scarb1(SR-BI) knockout mice. Methods: Patients who are candidates for PCI (coronary artery with ≥50% stenosis) were recruited at the Nagoya City University Hospital. Their blood was collected into a tube containing an LCAT inhibitor (NEM) and an anticoagulant. Blood from healthy volunteers was collected into tubes containing an anticoagulant. Scarb1 knockout mice were created as a disease model. Plasma FC and total-cholesterol(TC) were determined using an SF-CHO-N reagent (SEKISUI MEDICAL), and the LabAssay Cholesterol kit (Fujifilm), respectively. Results: Plasma FC were 0.344±0.08 mg/mL in the patient group(n=21, HDL-C 50.8±10 mg/mL, Lp(a) 19.3±21 mg/dL) and 0.40±0.09 mg/mL in the healthy group(n=27) (P=0.027). However, the FC/TC ratio was 32.3±5.1% in the patient group and 25.2±2.7% in the healthy group, with a significantly higher value observed in the patient group (P<0.0001). The FC/TC ratio in the top 23% of patients (n=5) was as high as 40.3±3%. In Scarb1 knockout mice and Scarb1/Apoa1 double knockout mice, the plasma FC/TC ratios were 58±8.6% and 60±5.8%, which were significantly higher than wild-type (21.5±8.2%). Conclusions: Deletion of the Scarb1, the HDL-C receptor, results in a significant increase in plasma FC/TC ratio. These results suggest that an elevated plasma FC/TC ratio in ischemic heart patients may be partially related to a characteristic of pathophysiological states associated with impaired HDL-C removal. Further fractionated analysis of plasma in patients with ischemic heart disease will be needed.