The object of aetiology is to unveil causes, conditions that are necessary (although not sufficient) for the occurrence of a disease. No authentic cause of atherosclerosis has been identified yet. So far, aetiologic research has only established risk factors, modifiable conditions that are neither necessary nor sufficient, which provide efficient but incomplete means for prevention. Other aetiologic tracks must be explored, where the levers for truly mastering atherosclerosis are to be found. Infection is but one example which is presently the object of keen interest, but remains quite far from definitive proof.