['The efficacy of lansoprazole (LPZ) at inhibiting gastric acid secretion is influenced by cytochrome P450 2C19 (CYP2C19) polymorphism. The purpose of the present study was to investigate whether CYP2C19 polymorphism had an influence on the remission of erosive reflux esophagitis (RE) during maintenance therapy with LPZ.', 'Eighty-two Japanese patients with initial healing of erosive RE by 8 weeks of LPZ therapy were enrolled. As maintenance therapy, the patients were treated with LPZ (15 mg/day) for 6 months. The CYP2C19 genotype, Helicobacter pylori infection status, and serum pepsinogen (PG) I/II ratio were assessed before treatment. The patients were investigated for relapse by endoscopy at 6 months or when symptoms recurred.', 'The proportion of patients in remission after 6 months was 61.5%, 78.0%, and 100% among homozygous extensive metabolizers (homo-EM), heterozygous EM (hetero-EM), and poor metabolizers (PM), respectively. The percentage of PM patients who remained in remission was significantly higher than that of homo-EM or hetero-EM.'] Does cytochrome P450 2C19 polymorphism influence the preventive effect of lansoprazole on the recurrence of erosive reflux esophagitis?