 This is a double-blind, randomized, placebo-controlled, crossover trial where 20 patients with confirmed persistent GERD symptoms at least twice weekly after a standard course of PPI, with abnormal bile reflux levels but normal esophageal acid exposure are randomized to initially receive either AST-120 or placebo for a period of 4 weeks after a two week screening period. After a washout period of one week, patients will cross over to the opposite blinded treatment. 