The concepts of acceleration of atherosclerosis with fat rich diets and the regression or at least stabilisation of atherosclerosis by suppressing the cholesterol, introducing exercise programmes or administering calcium antagonists or aspirin, have been validated in the animal model. In the clinical situation, repeat coronary angiography has demonstrated that hyperlipidemia and the interval between two investigations are the main factors influencing the progression of atherosclerosis. However, the factors underlying the appearance and progression of atheromatous plaques remain unknown. Interventional trials based on the principle of introducing treatment after reference angiography have been undertaken. The results were assessed after variable time intervals. The general conclusion is that there is a direct relationship between the lowering of plasma cholesterol, the intensity of exercise and the slowing of progression of atherosclerosis as far as can be evaluated by repeat angiography. The data concerning the effect of calcium antagonists is confusing. The main criticism of these trials is the instrument of measurement and the practical significance or even the reality of the observed changes. In the present state of our knowledge, trials of the regression of atherosclerosis can not replace longitudinal studies of the long-term effects of drugs on cardiovascular and general morbidity and mortality.