Diagnostic approaches such as angiography, ultrasound, computed tomography and nuclear magnetic resonance have limitation for contributing to the early clinical diagnosis of atherosclerosis. Recently, Tc-99m-labelled low density lipoprotein was developed to detect early atherosclerotic lesion by external imaging with gamma camera. To determine whether Tc-99m- LDL scintigraphy can visualize the active atherosclerotic lesion, rabbits were injected with Tc- 99m-LDL, 3 months after feeding dietary fat (lanolin) and we obtained following results. 1) Labelling efficiency of Tc-99m-LDL was 79∼88%. 2) Biodistribution study of normal rabbits with Tc-99m-LDL revealed the high activities in spleen, adrenal gland, liver, kidney which are major organs of high metabolic rate of LDL. 3) Three months after feeding lanolin, serum cholesterol was markedly increased from 74±17 mg/dl to 979±153 mg/dl and histologic study of aorta after sacrificing the rabbit demonstrated marked atherosclerotic changes. 4) Atherosclerotic lesion of abdominal aorta which was confirmed with histologic study could be demonstrated in Tc-99m-LDL scintigraphy after feeding lanolin for 3 months. In conclusion, the results of this preliminary investigation suggest that it may be possible to image active atheromatous lesion with Tc-99m-LDL. It is anticipated that this promising agent may allow the in vive monitoring of preclinical atherosclerotic lesions and may be useful to evaluate the metabolic path way of LDL in humans.