High resolution electrical mapping in the gastrointestinal system entails recording from a large number of extracellular electrodes simultaneously. It allows the collection of signals from 240 individual sites which are then amplified, filtered, digitized, multiplexed and stored on tape. After recording, periods of interest can be analysed and the original sequence of activity reconstructed. This technology, originally developed to study normal rhythms and abnormal dysrhythmias in the heart, has been modified to allow recordings from the gastrointestinal tract. In this report, initial results are presented describing the origin and propagation of the slow wave in the isolated stomach and the isolated duodenum in the cat. These results show that in both organs it not uncommon to have more than one focus active during a single cycle. The conduction of slow waves from such a multiple pacemaker environment can become quite complex, and this may play a role in determining the contractile pattern in these organs.