We developed a method to evaluate the severity of chronic cardiac failure by Doppler image analysis. Doppler images of the whole arterial lumen were consecutively recorded on video tape and the power spectrum (sum of intensity multiplied by frequency) of each frame was considered as an index of the blood flow volume (VI). The right brachial artery was occluded for 15-60 seconds by a occluding cuff, and was released quickly. The VI was determined until the VI returned to the level at rest and total VI was calculated as an O₂ repayment. The O₂ repayment rate (R-Rate) was calculated as a ratio of the O₂ repayment divided by total VI during interruption. The cardiac function was evaluated by sub-maximal exercise using bicycle ergometer and was compared with the R-Rate. The subjects were 22 patients (18 males and 4 females) with chronic cardiac failure of NYHA class I (9), class II (6), class III (4), class IV (3) and 12 healthy controls. R-Rate was almost unchanged by the duration of occlusion and showed positive correlation with exercise capacity. R-Rate decreased as the class of NYHA advanced. In conclusion, determination of reactive hyperemia can be used for objectively evaluating the severity of cardiac failure.