A short survey is presented of the homocysteine theory of atherosclerosis with the key role of endothelial injury. Hyperhomocysteinaemia is a newly emerging risk factor of atherosclerosis. Both hereditary and nutritional influences may contribute to its occurrence. As this risk factor concerns 30-50 percent of atherosclerotics, it may be expected that new methods making possible its detection will be developed and routinely used. Beside the determination of homocysteine blood levels some indicators of endothelial dysfunction such as endothelaemia after methionine load may be used in the future.