The proposed sensitivity of the DB-Bcg enables its gradation into four types-two normal, two abnormal. Their response to exercise shows specificity-amplified in the former, decreased in the latter. Illustrative material reveals deterioration of DB-Bcg forms with the earliest signs of cardiac symptomatology and is correlated with arteriographic evidence of coronary disease. This could not be corroborated either by the ECG, even post exercise, or changes in the PEP/LVET ratio. Improvement of the DB-Bcg following bed rest and/or therapy and by-pass grafting have been observed. Early application of the DB-Bcg, particularly in the young individual, may help meet the challenge of cardiac mortality.