An inverse correlation between the level of high density lipoprotein(HDL) and the risk of developing coronary artery disease(CAD) has been demonstrated in many previous epidemiological studies. To characterize plaque morphology in relation to HDL level, coronary angiography and intravascular ultrasound(IVUS) studies for measurements of diameter stenosis(DS), area stenosis(AS), plaque area(PA) and maximal plaque thickness(PT) were performed for 119 consecutive patients(age: 55짹10, 24 female and 95 male) with total cholesterol(TC) 186짹41 mg/dl, HDL 40짹10 mg/dl, LDL 112짹35 mg/dl, and triglyceride(TG) 167짹116 mg/dl, during cardiac catheterization for evaluation of stable angina. There were 28 patients(pts) with hypertension, 11 pts with diabetes mellitus, 19 pts with TC > 200mg and 52 smokers. All patients were divided into two groups depending upon HDL level, ie. group A(HDL < 40mg, N:66, 8 female, 58 male) and group B(HDL > 40mg, N:53, 37 male, 16 female). Therefore, it appears that lower the HDL level, PA is larger and PT is thicker, compared to patients with higher HDL level, resulting increased DS and AS in patients with lower HDL. There was no significant difference in plaque characteristics with 21 hard and 45 soft plaques in group A, and 18 hard and 35 soft plaque in group B. (P:NS). Thus, the level of HDL appears one of the important determinants which may affect the process of atherogenesis, resulting decreased plaque size in coronary artery, possibly through reverse transport mechanism.