A lead system was constructed to extract dipole and quadrupole components of cardiac sources from surface electrocardiograms (ECGs) recorded at 16 sites. The lead system was based on an analysis of a computerized model of a multipole equivalent cardiac generator in a homogeneous torso. The model was previously determined from extensive geometric and electrocardiographic data obtained from one subject. Dipole components estimated with the lead system were 89% accurate for the original subject. Evaluation of the lead system on this subject and in 59 other subjects included calculation of the effect of non-dipolar sources on the values of the estimated dipole components, comparison of the consistency of equivalent sources found independently at two origins in the heart region, and reconstruction of ECGs from lead system components. Dipole consistency at the origins was maintained over the wide range of age, weight, and body shape which characterized the subject population. Whereas quadrupole terms did not agree as well as the dipole terms, inclusion of the quadrupole reduced ECG reconstruction errors by a factor of about three compared to errors for the dipole alone. Together, the dipole and quadrupole accounted for almost 90% of the electrocardiographic information measured on the body surface with the D/Q lead system.