Although low-dose acetylsalicylic acid (ASA) is recommended for prevention of cardiovascular events in at-risk patients, its long-term use can be associated with the risk of peptic ulcer and upper gastrointestinal (GI) symptoms that may impact treatment compliance. This prespecified secondary analysis of the OBERON study (NCT00441727) determined the efficacy of esomeprazole for prevention/resolution of low-dose ASA-associated upper GI symptoms. A post hoc analysis of predictors of symptom prevention/resolution was also conducted. Helicobacter pylori-negative patients taking low-dose ASA (75-325 mg) for cardiovascular protection who had ≥1 upper GI risk factor were eligible. The patients were randomized to once-daily esomeprazole 40 mg, 20 mg, or placebo, for 26 weeks; 2303 patients (mean age 67.6 years; 36% aged >70 years) were evaluable for upper GI symptoms. The proportion of patients with dyspeptic or reflux symptoms (self-reported Reflux Disease Questionnaire) was significantly lower (P < 0.0001) in those treated with esomeprazole versus in those treated with placebo. Treatment with esomeprazole (P < 0.0001), age >70 years (P < 0.01), and the absence of upper GI symptoms at baseline (P < 0.0001) were all factors associated with prevention/resolution of upper GI symptoms. Together, these analyses demonstrate that esomeprazole is effective in preventing and resolving patient-reported upper GI symptoms in low-dose ASA users at increased GI risk.