In this study, patients over 18 years of age presenting with GERD symptoms to a primary care physician, will be recruited after providing informed consent. Patients will perform a sucrose leak test the evening after their recruitment by drinking a solution of 100 gms of sucrose in 200 cc of water at bedtime, then collecting an overnight urine sample (8 hrs). Within 5 days the patient will undergo an upper endoscopy exam. The patient will then begin Nexium therapy (40 mg/day of Esomeprazole) for 8 weeks, taking the dose each morning before breakfast. After 8 weeks the patient will undergo a second sucrose leak test as described above. Urine sucrose will be determined by HPLC.