The effect of closely spaced swallows to decrease peristalsis ('deglutitive inhibition') is believed to be due to both central inhibitory impulses and smooth muscle refractoriness. Ten volunteers (three females, age 26-65) were given both four pairs and two series of four swallows at 5-, 10-, 15-s intervals and control swallows at 30-s intervals. Oesophageal function was assessed using combined multichannel intraluminal impedance and oesophageal manometry (MII-OM). Swallows were considered manometrical effective if distal oesophageal pressures >/=30 mmHg. Complete bolus transit was defined as bolus exiting from all three distal impedance segments. During swallowing at 5-s intervals the majority of initial swallows were ineffective with incomplete bolus transit while the last swallow in both series and pairs was manometrically effective with complete bolus transit. During swallowing at 10-15-s intervals the number of manometric ineffective swallows and swallows with incomplete bolus transit progressively increased with the number of swallows. The functional information obtained by MII-OM indicates pooling of liquid in the distal oesophagus that is cleared by the last swallow determined by, previously reported, neural inhibition occurring during swallowing spaced 5 s apart whereas incomplete bolus transit is related to manometrically ineffective swallows resulting from muscle refractoriness occurring during swallowing at 10-15-s intervals.