Background/Aims: Esophageal reflux damage may be produced by agents other than acid and the term alkaline esophagitis has been applied. Methods using esophageal pH monitoring to assess duodenogastroesophageal reflux have been suggested but gastric neutralization has made these methods difficult to prove conclusively. The purpose of this study were to investigate the role of duodenogastroesophageal reflux in gastroesophageal reflux disease(GERD) and to understand the relationship between pH and duodenogastroesophageal reflux. Methods: we performed simul- taneous esophageal pH and bilirubin rnonitoring(Bilitec 2000, Synetics) in 14 symptomatic patients with gastroesophageal reflux and 10 healthy controls. Abnormal gastroesophageal reflux was defined when the percent total time of pHC4 or bilirubin absorbance 0.14 exceeded the 95th percentile of the range obtained in healthy volunteers. Results: Abnormal gastroesophageal reflux was diagnosed in 12(85.7%) of 14 patients, who could be categorized into 3 acid refluxers, 1 bile refluxer or 8 combined acid and bile refluxers. All 6 patients with severe esophagitis(grade 2 by Savary Miller classification) were combined acid and bile refluxers and had markedly prolonged acid and bile reflux compared to 8 patients with normal or mild esophagitis(% total time of pH 4(mean+SE): 13.4+2.96 vs 5.0+1.8, p<0.05; % total time of bilirubin absorbance 0.14(mean+SE): 25.2+4.6% vs 7.9+3.8%, p<0.05). Mean pH of esophageal refluxate during bile reflux episode lasting longer than 5 minutes was 6.0(7.1% for pH C4, 8.8% for pH 4 5, 26.6% for pH 5-6, 47% for pH 6-7 and 8.3% for pH7). 4) 8 patients with a symptom index greater than 25% experienced 24 reflux symptoms of which 12(50.0%) were associated with acid reflux, 5(20.8%) were associated with bile reflux and 7(29.2%) were not associated with bile or acid reflux. Conclusions: Alkaline esophageal reflux is a misnomer. Esophageal pH monitoring does not adequately identify symptomatic non-acidic duodenogastroesophageal reflux. Patients with com- bined acid and bile reflux are more likely to develop severe esophagitis. (Korean J Gastroenterol 1996; 28:469 - 476)