INTRODUCTION: The impact of prescription NSDAIDS on the GI tract is well documented. The easy availability of low-dose OTC NSAIDs may lead to iatrogenic GI disease invisible to the medical community. OBJECTIVE: To determine role and rate of GI adverse side effects were related to over-the-counter NSAID use. METHODS: Data were obtained by structured telephone survey administered to a nationally representative, randomly selected US adult population (>40 years). We compared responses of regular OTC NSAID users (defined as use for at least 4 of 7 days, and 16 of 30 days prior to the survey) with those of non-users. Logistic regression compared the likelihood of GI symptoms and use of GI medications, after adjusting for age, gender, ethnicity, and self-reported health status. RESULTS: We surveyed 535 OTC NSAID users (mean age=63, range 40-96) and 1068 non users (mean age=63, range 40-93). NSAID users were 2.1 times more likely to report GI symptoms than non users (p=0.0001), and 2.7 times more likely to have taken OTC GI medications than non users (p=0.0001) during past 30 days. 84.8% of NSAID users taking GI medications for their symptoms had not informed a physician of GI symptoms. CONCLUSIONS: OTC NSAIDs are widely used and thought to be safe at low dose. Our data show users commonly experience GI symptoms, for which they self-medicate without informing their physician. This may represent an important burden of hidden GI disease.