Reflux oesophagitis is a common clinical disorder associated with significant morbidity. Proton pump inhibitors are the current pharmacotherapy of choice, but not all treated patients achieve symptom relief. Little is known about the efficacy of mosapride, a prokinetic agent which decreases episodes of gastro-oesophageal reflux, as an adjunct to proton pump inhibitors in improving the symptoms of reflux oesophagitis. WHAT THIS STUDY ADDS Mosapride was generally not more effective than placebo as an adjunct therapy to a standard dose of lansoprazole in decreasing the symptom burden of patients with reflux oesophagitis. However, in a subgroup with more severe symptoms, combination therapy with lansoprazole and mosapride was possibly superior to monotherapy with lansoprazole. AIMS To investigate if mosapride, a prokinetic agent, was an effective adjunct to acid suppression in improving the symptoms of reflux oesophagitis. METHODS Patients (n = 96) with reflux oesophagitis were randomly assigned to either mosapride (5 mg three times daily) or placebo for 4 weeks. Symptom severity was assessed by a validated questionnaire at enrolment, 4 and 8 weeks after medication. The primary outcome for the first 4 weeks was decrease in symptom scores. After a 3 day washout period, patients initially allocated to mosapride crossed over to placebo and vice versa for the next 4 weeks. The outcome of the second phase was maintenance of symptom control. All patients received lansoprazole (30 mg once daily) throughout study. RESULTS The decreased symptom score after 4 weeks of treatment with lansoprazole and mosapride (n = 50) was 13.42 1.16 (mean SEM), similar to that of lansoprazole plus placebo (10.85 1.03, n = 46), with an insignificant difference of 2.57 (95% CI-0.53, 5.67, P = 0.103). However, a subgroup analysis for patients with pre-treatment scores of >18 points (n = 48) revealed that lansoprazole plus mosapride achieved a greater reduction of symptom score than lansoprazole plus placebo (18.22 1.91 vs. 12.88 1.65; mean difference of 5.34, 95% CI 0.28, 10.40, P = 0.039). In the second phase, there was no difference between lansoprazole with mosapride or placebo in maintaining symptom control (39/44 or 86.64% vs. 41/50 or 82%, P = 0.401). Subgroup analysis for those with substantial residual symptoms revealed similar results. CONCLUSION Compared with placebo, mosapride generally does not provide additional benefit to a standard dose of lansoprazole in patients with reflux oesophagitis, except possibly in the subgroup of severely symptomatic patients.