A simple method to determine the state of ischaemia or fibrosis of myocardial cells has been developed. This method uses the ST wave of 64-channel magnetocardiogram (MCG) signals to calculate three parameters from the current-arrow map of the normal component signal of the MCG. One parameter is a total current vector that is obtained through summation of all current arrows. Another is a variance current vector calculated from the differential vector of two total current vectors at different times. The third is a flatness factor between the magnitude of the total current vector and the variance current vector. The three parameters are independent of the distance between the heart and the gradiometers. We measured the MCG signals of 29 healthy subjects, twenty patients with coronary artery disease (ten with previous myocardial infarction (MI) and ten with angina pectoris (AP)), and eight patients with cardiomyopathy (four with hypertrophic cardiomyopathy (HCM), three with dilated cardiomyopathy (DCM), and one with restrictive cardiomyopathy (RCM)). With our method, none of the healthy subjects tested positive for myocardial abnormalities, while 80% of the MI patients, 50% of the AP patients, and 100% of the cardiomyopathy patients tested positive. Although further testing is needed, we feel this simple technique enables easy diagnosis of myocardial damage.