In a phase III study of lansoprazole treatment, patients with healed or unhealed erosive esophagitis entered a titrated open-label treatment period and received lansoprazole for <or=6 years to assess long-term maintenance therapy. Doses were adjusted depending on symptom response. Endoscopy was performed yearly. One hundred ninety-five subjects received lansoprazole for <1 to 72 months; most received daily doses of <or=30 mg. Lansoprazole maintained erosive esophagitis remission in 75% of subjects receiving treatment for <or=72 months, with 39 subjects experiencing 50 recurrences. Most subjects (94-95%) had no or mild symptoms of day or night heartburn at study end, and 77% were asymptomatic at first erosive esophagitis recurrence. The most common treatment-related adverse events included diarrhea (10%), headache (8%), and abdominal pain (6%), and were mild or moderate in severity. Long-term lansoprazole is effective and well tolerated when used to maintain erosive esophagitis remission for <or=6 years.