High resolution body surface potential maps (BSPM) and magnetic field maps (MFM) for study groups consisting of 11 Q wave and 11 non Q wave myocardial infarct (MI) patients as well as 9 normal subjects, were recorded in a magnetically and electrically shielded room. A control group of 22 normal subjects provided group mean normal time integral maps for selected QRST time intervals. The difference between magnitudes of extrema in each map defined the normal mean data range R for that time interval. The root mean square sum of the differences between the time integral map of a study subject and the normal group-mean map provided an estimate of individual map variability, V. Subsequent calculation of group-mean map variability, V, and group-mean normalized variability, V/R, for specific time intervals of the cardiac cycle, were used to test the abilities of BSPM and MFM techniques to distinguish between the normal and MI study groups. Results indicate that BSPM V/R differences between MI and normal groups are most pronounced during Q wave and Q zone activity; between inferior MI's and normals (p less than 0.05) and between anterior MI's and normal (p less than 0.01). Significant differences in MFM V/R occur during repolarization; between inferior MI's and non Q wave MI's (p less than 0.05), between anterior MI's and normals (p less than 0.05), between non Q wave MI's and normals (p less than 0.05) and between all MI's and normals (p less than 0.01). It is concluded that high resolution BSPM and MFM provide complementary means of discriminating between normal subjects and MI patients.