One hundred body surface isopotential maps for 30 normal infants, ages three hours to seven days, were evaluated. Ventricular activation and recovery were examined. In the early and mid phase of QRS, the maximum moved from the center of the anterior chest to the lower right portion of the anterior chest. In the late phase, the maximum appeared on the back. The niche appeared earlier in normal newborn infants (19.6 +/- 3.9 msec) (mean +/- S.D.) than in normal children (25.7 +/- 4.6 msec) (P less than 0.001). The location of the maximum at the time of peak positive potentials gradually shifted leftward during the first week of life. The 100 T wave maps were classified into three types. During the first day of life, the T wave maps showed type I or II, changing to type II or III a few days after birth. All T wave maps were type III a week after birth. The ratio of type III gradually increased with age. We found that the QRS maps were different from those of normal children and that T wave maps changed within the first week of birth.