The normal range of body surface isopotential mapping was investigated in 176 healthy Japanese volunteers (93 males and 83 females). Mean maps of the QRS wave were prepared on the basis of sex and age. In addition, analyses were made of the differences in relation to the maximum positive potential and the maximum negative potential for each induction point, the breakthrough recognition rate and the breakthrough recognition time as a function of sex and age. With regard to the temporal changes in the map after the initiation of ventricular stimulation, no differences were seen in the pattern of the distribution of the zero potential line or the positions of the peaks and troughs as a function of sex and age. In every age group, both the positive and negative potentials were larger in males than in females. There was a tendency for the breakthrough recognition rate to decrease with increasing age in both the male and female subjects. No differences were detected in the breakthrough recognition time as a function of sex and age. The range of the time was 21.3±5.8~29.7±7.4msec (mean 25.6±6.3msec). The breakthrough minimum recognition time ranged from 24.4±6.4 to 33.0±6.6msec (mean 29.2±7.1msec).Comparison was made of the maximum positive potential and maximum negative potential at each of the 87 induction points as a function of sex and age. With regard to the maximum positive potential, a tendency to decrease was seen from the left anterior chest area to the back in the males with increasing age. Conversely, in the females, there was a tendency for the maximum positive potential to increase from the left anterior chest area to the left lateral chest area with increasing age. The maximum negative potential tended to decrease in the anterior upper chest area with age in both the sexes, while in the anterior lower chest area this potential tented to increase with age in both sexes.In view of the above results, when employing body surface isopotential mapping to diagnose various types of heart disease, it can be concluded that it is necessary to perform the diagnosis on the basis of normal standards which take into consideration the sex and age of the patient.