Aim: To evaluate the oesophageal function in patients with different types of oesophageal metaplasia and in cases with dysplasia on the basis of the Montreal definition of gastro-oesophageal reflux disease. Patients and Methods: 270 consecutive patients [M/F 151/119, mean age 54.2 years (19–84)] with endoscopic and histological evidence of oesophageal metaplasia were prospectively studied: patients with specialized intestinal metaplasia (SIM, n = 109) and patients without SIM (n = 161). Patients with SIM were subdivided into a dysplasia-positive (n = 34) and a dysplasia-negative (n = 75) group. All patients underwent reflux symptom analysis, oesophageal manometry, and simultaneous 24-hour pH and biliary reflux monitoring. Results: Patients with SIM were significantly older and had a significantly higher body mass index than patients without SIM. A significant male predominance was observed in patients with SIM and dysplasia compared to the dysplasia-negative group. The clinical symptom spectrum and the prevalence of erosive oesophageal lesions were similar in all groups. Patients with SIM had longer metaplastic segments, which was further increased in the dysplasia-positive group. During oesophageal manometry, pH and biliary reflux monitoring, patients with SIM had more severe alterations than patients without SIM, and these were further increased in patients with SIM and dysplasia. Conclusions: Patients with SIM had more severe oesophageal function abnormalities than those with other types of oesophageal metaplasia (e.g. gastric). The oesophageal function was further impaired if dysplasia was present in the metaplastic mucosa.