This paper presents a multipole analysis of the QRS complex of the normal magnetocar-diogram (MCG) of six normal subjects. The multipole strengths up to the octupole term were determined from the measured distribution of the z-component of the cardiac magnetic field (the component perpendicular to the frontal plane). This equivalent magnetic multipole generator was found to represent the cardiac magnetic field with a minimum error of <10%. The dipolar term of the expansion was found to represent the field distribution with reasonable accuracy early during ventricular activation, whereas late during activation, the higher multipole terms were clearly more significant.CircRes 47:117-130, 1980