The efficacy of cricoid pressure was studied in 10 adult cadavers. The oesophageal pressure that would result in regurgitation during measured values of cricoid pressure was determined. Oesophageal pressure, recorded by a 2 mm diameter oesophageal tube, was increased by oesophageal distension with saline, and incremental levels of cricoid force, 20, 30 and 40 Newtons, were applied with a cricoid yoke. With each 10 Newton increment of cricoid force there was a significant rise in the oesophageal pressure required to provoke regurgitation (p < 0.01). Thirty Newtons of cricoid force prevented regurgitation of saline in all cadavers with oesophageal pressures of up to 40 mmHg. Rupture of the oesophagus occurred in three cadavers: one at 30 and two at 40 Newtons of cricoid force, but there was no rupture at 20 Newtons of cricoid force. In the other seven cadavers oesophageal pressures were also studied with a 4.6 mm diameter (14 FG) oesophageal tube, which did not reduce the efficacy of cricoid pressure in preventing regurgitation.