OBJECTIVES: To show the efficacy of orally administered esomeprazole 40mg (ESO) in patients with erosive gastro-oesophageal reflux disease (GERD) in Mexico. METHODS: We conducted an open label, prospective cohort study in 22 centers in Mexico, between June 2001 and July 2002, with patients being 18 – 86 years old, diagnosed with endoscopy-confirmed erosive (GERD) and classified according to Los Angeles Classification (LAC). Patients were treated with ESO 40 mg for a 4-8 week period. According to LAC, effectiveness was measured by the reflux-oesophagitis healing at 4 and 8 weeks, defined as the absence of macroscopic mucosal lesions. Symptoms and general evaluation of the treatment were secondary end points. Presence of Helicobacter pylori was assessed by clotest. The study was analyzed using the ITT population. Healing at the 4 and 8 week endpoints was assessed with the McNemar test (p<0.05, 95% CI). RESULTS: A total of 213 patients were included in the study: 53.52% were males, and the average age was 44.2 years (±14.63). 78.88% were diagnosed with mild to moderated GERD (Grades A & B LAC), and 38.97% were positive for Helicobacter pylori. Using gastro-oesophageal endoscopy as the assessment method, GERD healing rate after the 4 and 8 weeks period with esomeprazole 40 mg were 88.73% (84.48%-92.98%, 95% CI) and 94.84% (91.87%-97.81%, 95% CI) respectively. No serious adverse events were reported. Treatment with esomeprazole 40 mg was well tolerated. CONCLUSION: Esomeprazole 40 mg proved to be effective and secure for the GERD treatment in the Mexican patients.