Objective To observe the typical ECG appearance of the inbred MIJ and HFJ rats and compare with that of Wistar rats. MethodsSix of each gender and strains of rats were selected as one group. The rats were anesthetized and fixed on a board. A needle electrode pierced into the skin about 2—3 mm. FX-102B ECG device was applied to perform the ECG record. ResultsAs same as that of Wistar rats, both the male and female MIJ and HFJ rats showed a sinus rhythm, and the heart rhythm was regular. No marked differences were showed between the genders and the MIJ and HFJ rats. However, compared with the male Wistar rats, the heart rate of male HFJ and MIJ rats was higher. The electrical axis of heart in HFJ and MIJ rats was as the same as that of the Wistar rats, mostly ranging from 0°—90°. All characteristics of P-waves and QRS waves in the HFJ and MIJ rats were the same as that of Wistar rats. But there were apparent differences in the amplitude and periods of different waves between the strains and genders. ConclusionThere are characteristic ECG manifestations in inbred MIJ and HFJ rats.