Blood lymphocyte energy metabolism was assessed in coronary patients. Among intracellular adenine nucleotides, ATP was shown to be particularly prone to change, declining in proportion to the progress of the disease in all patients. ADP (1st functional class, or FC) and AMP (1st and 3d FC) declined less markedly. Atkinson's energy potential remained stable, although reduced significantly in patients of the 3d FC. Lymphocyte glycolytic activity was significantly lowered in patients of the 3d and 4th FC. Possible mechanisms of blood lymphocyte energy disorders, associated with coronary heart disease, are discussed.