Gastroesophageal reflux disease (GERD) often is associated with pulmonary problems such as asthma as well as recurrent and nocturnal cough. Dual-probe 24-hr pH monitoring may assist in establishing a correlation between these symptoms and GERD-related symptoms. To determine if any specific symptom was predictive of aspiration, this study was undertaken. Ambulatory dual-probe esophageal pH monitoring was performed on 133 patients who had upper airway and additional symptoms for GERD. All patients had esophageal manometric studies of the lower esophageal sphincter (LES), the upper esophageal sphincter (UES), and the esophageal body before dual-probe pH monitoring was performed. Using two assembled glass probes, the distal and the proximal sensors were placed 5 cm above the proximal border of the LES and 1 cm below the lower border of the UES, respectively. Patients were classified into three groups: proximal and distal probe positive (group I), proximal probe negative and distal probe positive (group II) and proximal and distal probe negative (Group III) Upper airway and additional symptoms plus manometry results of the LES, body and UES study were compared between groups. In addition, positive distal probe patients (groups I and II) were compared for distal fraction of time at pH < 4 and number of reflux episodes at each probe position. A positive distal probe result was defined as an abnormal DeMeester score (> 14.8). A proximal probe test result was considered positive if percent time pH < 4.0 was > 1.1 for total, 1.7 for upright, and 0.6 for supine positions. The ages of the subjects ranged from 18 to 83 years (mean age: 50.5 +/- 1.5 years). Groups I, II, and III included 16 patients, 38 patients, and 79 patients, respectively. Group I had a significantly higher incidence of nocturnal cough than the other two groups. (P < 0.05). The manometric data revealed between groups that LES pressure (LESP) for groups I and II was significantly lower than LESP for group III (P = 0.003). Cricoid pressure, pharyngeal pressure, length, and relaxation of UES were not different between groups. Fraction of reflux time for group I was significantly higher than for group II in the supine position and at mealtime (P < 0.05). The number of reflux episodes for group I was significantly higher at meal time (P < 0.01). In conclusion, nocturnal cough is strongly predictive of proximal esophageal reflux. Proximal reflux episodes are significantly more frequent in the supine position and correlate well with the high predictive value of nocturnal cough.