Inclusion Criteria:

• Patients must have had a minimum three-month history of symptomatic GERD, with heartburn as the predominant symptom, and must report nocturnal heartburn symptoms (i.e., heartburn symptoms experienced during the night-time period, between 2200 and 0600h)
• Patients must currently be taking a proton-pump inhibitor (PPI) or histamine-2 receptor antagonist (H2RA) at least four weeks prior to study admission
• Patients must be able to read, write and understand the language of the HRQOL and productivity assessment instruments (PAGI-SYM, PAGI-QOL, WPAI-GH) i.e., English or French
• Patients must have been at least 80% compliant with their current acid suppressive therapy, and must have completed a minimum of 11 of 14 nocturnal heartburn ratings during the run-in period (i.e. <=3 "missing" nocturnal heartburn ratings during the 14-day period)
• Patients must have a total nocturnal heartburn symptom score of >4 points during the 2-week run-in period
• 3 "missing" nocturnal heartburn ratings during the 14-day period) as recorded in the diary
• Night-time heartburn control assessment of "very dissatisfied, dissatisfied, neither dissatisfied nor satisfied" at the end of the 2-week run-in period

Exclusion Criteria:

• Patients currently taking rabeprazole 20mg once daily (morning or evening administration) or 10mg twice daily (morning and evening administration) on a continuous basis
• Documented evidence of GERD refractory to acid suppressive therapy (i.e
• No or poor clinical response to at least two treatment courses of 4-weeks duration with a PPI)
• Esophagitis known to be the result of systemic events (e.g. scleroderma, ingested irritants)
• Active GI bleeding, or presence of "alarm symptoms" (i.e., vomiting, blood in stool, anemia, dysphagia)
• Documented history of significant pyloric stenosis or esophageal ring stricture
• Documented evidence of esophageal or gastric varices
• Patients with primary motility disorders, infectious or inflammatory conditions of the small or large intestine, malabsorption syndromes, GI obstruction, history of gastrointestinal malignancy, definitive acid-lowering surgery or other esophageal, gastric or intestinal surgery (including vagotomy) except for simple closure of perforation
• Patients who are unable or unwilling to discontinue the use of prostaglandins (e.g. misoprostol), sucralfate, prokinetic agents (e.g. metoclopramide), anticholinergics, cholinergic agents or spasmolytics. Use of opiates may be continued if started at least 2 weeks before study admission and the dosage is consistent (± 25% for total opioid daily dose) throughout the study
• Treatment with high-dose systemic corticosteroids (>10mg/day prednisone equivalent) and NSAIDs, including COX-2 selective inhibitors, cannot be initiated at anytime during the study. However, patients taking corticosteroids and NSAIDs (including ASA) before study entry may continue these medications during the study, however, they must have been taking a stable dose (e.g. for oral medication, a consistent daily dose ± 25%) for at least 2 weeks before study admission and the dosage must be kept constant throughout the study. Occasional, intermittent use of NSAIDs for acute, self-limiting conditions (e.g. headache relief) is acceptable during the study
• >3 daytime episodes during any 7 consecutive days of the run-in period
• >1 severe or very severe daytime episode (i.e., more than 1 daytime heartburn episode rated >=3) during any 7 consecutive days of the run-in period
• Maximum total daytime heartburn score >5 during any 7 consecutive days of the run-in period