As a procedure to accelerate healing of the bone defect, the electric micro-current has attracted much attention in the field of clinical application and experimental research. However, investigation of the calcifying process and comparison of the elements of the newly formed bony callus have not yet been carried out. In order to get deeper understanding of the callus formation and calcifying process in bone defects, this experiment aimed at comparing the healing processes of bone defects in the rabbit humerus between stimulated and non-stimulated control group. The bone specimens were surgically removed, on the 4th postoperative day and 1st, 2nd, 3rd, and 4th postoperative weeks. The specimens were examined by the use of the computer aided microanalyser, the energy dispersive spectrometer, and the scanning electron-microscope (JCMA-733). Histological examination was also made. In the stimulated group, on the 4th day, Ca and P of low concentration were observed around the inner periosteum indicating initiation of the calcification with callus formation. On the 1st week Ca and P were distributed diffusely in the bone defect. On the 2nd and 3rd weeks, the bone defect was almost filled with new bony callus and the calcification became more intense. After the 4th week, the distribution and concentration of Ca and P in the bony callus were similar to those of the surrounding cortical bone. Furthermore, the molar ratio of Ca/P of the new bony callus was much greater in the stimulated group than in the control group, and was rather similar to the molar ratio of Ca/P in the surrounding cortical bone. The results showed that the electric micro-current facilitated not only callus formation but also calcification, thus shortening the healing period of the bone defect.