The temporal relationship between the slow wave and the spike bursts was studied in the fasted and the fed states in conscious dogs implanted with serosal electrodes on the jejunum. A fully automatic computerized method processed more than 225 h of recording. For each slow wave cycle that contained a spike burst, the program computed the cycle duration and the times elapsed from the beginning of the cycle to the onset and to the end of the burst. In the fasted state as well as after feeding, the spike bursts began and ended at any time within the segment of the slow wave cycle on which spike activity occurred. These results indicate that in vivo in the dog jejunum, the temporal relationship of the slow wave and spike bursts is not fixed. They suggest that the slow wave allows the spikes to occur during limited time intervals, but does not determine their precise location and duration within these intervals. Furthermore, differences existed in the patterns of the slow wave and in its relationship with spike activity (period, location, and duration of the segment on which the spike bursts occurred) between the various phases of the migrating myoelectric complex in the fasted state and the fed state.