A concept of pathogenesis of atherosclerosis is presented in which atherogenesis has been sharply delineated from the subsequent evolution of lesions to the stage of clinical disease. Basic to atherogenesis are active metabolic processes, presumably under the control of both local and systemic factors, on the part of mesenchymal cells in the inner layers of the arterial wall. Occurrence of early lesions in all subjects beyond the age of three years and the persistence of these lesions in a potentially reversible form for a period of many years has indicated that the problem is basically a pediatric one. A modus operandi for reversibility, namely “dispersion of lipid,” is illustrated; and a hope for fundamental control of the process is sounded.