AbstractRectal electrical activity, measured by electrorectography (ERG), was studied in 18 patients with chronic proctitis (11 ulcerative and 7 bilharzial proctitis). Mean age was 36.6±9.4 (SD) years. Eight healthy volunteers were included as controls. Monopolar recordings were made from silver‐silver chloride electrodes situated 1 cm from the tip of the catheter, which was applied to the rectal mucosa. Signals from the electrode were displayed on a U‐V recorder. Rectal neck and rectal pressures were recorded simultaneously. Pacesetter potentials (PP) were also recorded from all subjects. The healthy volunteers had a mean frequency of 2.6±0.6 cycles per minute (cpm), an amplitude of 2.4±0.5 mV, and a velocity of 4.3 ± 0.5 cm/sec. The potentials had the same frequency and regular rhythm when the test was repeated and were followed randomly by bursts of action potentials (AP). The rectal pressure increased simultaneously with the AP. In the proctitis patients the PP frequency was higher than normal (mean 8.2 ±1.6 cpm in patients with bilharziasis and 8.9 ± 2.1 cpm in those with ulcerative proctitis) (p<0.001), whereas the amplitude and velocity were lower than normal (p<0.05 andp<0.01, respectively). APs had higher frequency and amplitude and were accompanied by higher rectal pressure than in the normal volunteers. The increased PP, or tachyrectia, may be due to rectal wall or rectosigmoid pacemaker irritation caused by proctitis, whereas the diminished amplitude and velocity may be caused by a diseased rectal wall. The increased AP frequency and amplitude seem to cause increased rectal contractile activity with a resulting tenesmus. ERG is safe, noninvasive, nonradiologic, and it may prove helpful for diagnosing proctitis.