Cells of human aorta were isolated by dispersing the tissue with collagenase and elastase. The isolated cells were stained in suspension by the acridine orange fluorescent stain. The intensity of red fluorescence (>580 nm) corresponding to the RNA content was measured in each individual cell and registered in a FACS II flow cytofluorometer. It was established that a cell population of human aorta is heterogenous with respect to RNA content. In a population of isolated cells, one can distinguish two subpopulations: (A) small cells with low RNA content, and (B) large cells with high RNA content. The ratio of both cell types varies in intima and media, and different types of atherosclerotic lesions. The share of cells belonging to subpopulation A is lower in media compared to intima. In intima, the number of these cells grows with the degree of atherosclerotic lesion. Possible reasons for the discovered metabolic heterogeneity of human aortic cells and prospects for the application of flow cytofluorometry to a research into cellular mechanisms of atherosclerosis is discussed.