To evaluate the oesophageal motor activity preceding episodes of reflux, 10 pathological and 10 non-pathological refluxers and 26 normal subjects were investigated. The pressure events in spontaneous short periods of pressure activity (less than or equal to 60 sec) and in long activity periods were registered. The last contraction before reflux was more frequently found non-propagating than the last contraction of pressure periods not followed by reflux (p less than 0.01). The interval from the last contraction to reflux was shortest, if the contraction terminated in, or confined to the upper part of the oesophagus (p less than 0.001). Increased proportion of reflux episodes were preceded by an upper segmentary contraction (p less than 0.05) and a short activity period (p less than 0.02) in patients with pathological reflux in comparison with non-pathological refluxers. Spontaneously occurring sphincter relaxations might be triggered by preceding non-propagated contractile activity. The relative number of reflux episodes preceded by non-propagated pressure activity seems to be increased in patients with frequent episodes of acid reflux, compared with patients with infrequent episodes, or with normal subjects.