To investigate the temporal progression of atherogenesis on the aorta and involvement of the monocyte-macrophage system in the liver and spleen, we fed 74 rabbits with high fat (14 or 7 gm%) and cholesterol (2 and 1%) diets for 4 to over 24 weeks. Using both light and electron microscopies, we found that the bro-fatty areas on the luminal surface of aortas was spread over along the eding time dependently. The fat deposits also in the liver and spleen worsened pending on the time of feeding the atherogenic diets. Not only nocyte-derived foam cells, but also parenchymatous cells in the liver and leen involved become fat-laden cells. According to these results, we propose at there are three stages: 1) the primary seeding, 2) the intermediate turing and 3) the advanced periods. These periods may play very important les in designing the management and treatment of atherosclerotic patients.