BACKGROUND: Impedance-pH monitoring is the most sensitive method for detection and characterization of gastro-oesophageal reflux episodes. Normal values from European subjects are lacking. AIM: To build a database of gastro-oesophageal reflux patterns from French and Belgian healthy subjects. METHODS: Seventy-two healthy subjects (35 men, mean age 35 years, 18-72) underwent 24-h ambulatory impedance-pH studies. Gastro-oesophageal reflux episodes were detected using impedance and characterized by pH as acid, weakly acidic, or weakly alkaline. Analysis was performed visually and effects of age, gender and intra-individual reproducibility were evaluated. RESULTS: The total number of gastro-oesophageal reflux episodes was 44 (25,58,75) of which 59% were acid, 28% were weakly acidic and 10% weakly alkaline. Half of gastro-oesophageal reflux episodes were mixed (liquid/gas) and 22% reached 15 cm above the lower oesophageal sphincter. The bolus clearance time was 11 s while acid was chemically cleared in 34 s. Male gender was associated with increased number and proximal extent of total and acid gastro-oesophageal reflux. Repeated studies in 27 subjects showed good reproducibility for number, acidity and air-liquid composition of reflux (Kendall's W-values = 0.72-0.85). CONCLUSIONS: This study demonstrates good reproducibility of 24-h ambulatory impedance-pH studies and provides values of reflux patterns in healthy subjects for comparisons with European gastro-oesophageal reflux disease patients.