Abstract: Intestinal ischemia is diagnosed non-invasively by scanning the abdomen externally with a SQUID magnetometer which measures the magnetic field produced by smooth muscle electrical activity. These measurements are processed to determine the basic electrical rhythm (BER) frequency at various locations along the intestine. A nominal value for the BER frequency is established at each location, and if the measured value falls below the associated nominal value by more than a predetermined margin, ischemia at that location is indicated. Ischemia is further indicated by an interval of arrhythmia in which the BER frequency increases to a range of about 24-180 cpm or at least about twice the nominal value. The BER frequency values are presented on a graphic display which provides an indication of the nominal value at an affected location from the gradient of the measured values at adjacent normal locations.