Cholecystokinin (CCK) release in seven conscious dogs was investigated by means of modified sham feeding. After sham feeding mean CCK concentrations rose from a basal value of 1.0 +/- 0.2 pmol/l to a peak value of 2.4 +/- 0.3 pmol/l (p less than 0.005). The release in response to sham feeding amounted to half of that seen after normal feeding. Atropine significantly altered CCK output after sham feeding (basal, 1.0 +/- 0.2 pmol/l; peak 1.3 +/- 0.3 pmol/l). Sham feeding did not affect neurotensin release. It is concluded that an important cephalic phase of CCK release exists which seems to be dependent on a cholinergic mechanism.