Abstract: The present invention relates to method of treating a gastrointestinal motility disorder in a subject in need of treatment comprising coadministering to said subject a first amount of a compound having 5-HT3 receptor agonist activity or a pharmaceutically acceptable salt, hydrate or solvate thereof; and a second amount of at least one gastric acid suppressing agent (e.g., a proton pump inhibitor, an H2 receptor antagonist or a pharmaceutically acceptable salt, hydrate or solvate thereof; or an acid pump antagonist or pharmaceutically acceptable salt, hydrate or solvate thereof) wherein the first and second amounts together comprise a therapeutically effective amount. In particular, the method is for treating GERD, including nocturnal GERD.