A single-dipole model and a two-dipole model have been examined to approximate the electrical activity of heart; positions as well as vector components of these dipoles were estimated from the body surface potential distribution that was measured with 64 electrodes arranged on the chest. The "residue" has been defined as a measure for how much potential component is left that cannot be attributed to the equivalent dipoles. A locus of the vector end of an equivalent dipole in the single-dipole model is very much like ordinary vectorcardiogram (VCG). The residue has a peak in the last half of QRS; this means that the single-dipole approximation is not valid there. Then another dipole is introduced, which is the two-dipole approximation. The residue has been greatly reduced and the peak disappears; the resultant two dipoles move around in the right and left parts of the heart with nearly opposite directions. The moving-two-dipole model for normal subjects describes the cardiac activity in QRS much better than with the moving-single-dipole model.