Warm stimulation of a circumscribed region of the dorsal abdominal wall of the rabbit evoked discharges in splanchnic afferent single fibers. They showed positive temperature coefficients of their static activities and of their dynamic responses to temperature changes. They were not excited by mechanical stimuli. Cooling from static conditions caused a transient inhibition of impulse frequency. Two populations were found, one having a static and dynamic maximum at 46 degrees C, the other one at about 40 degrees C. Both types were found to be C-fibers, with a conduction velocity of 0.6 - 1.1 m/sec.