Proton pump inhibitors (PPIs) are the most potent drugs for reducing gastric acid secretion; so, since their release in the late 1980s, they have been recommended as the first therapeutic choice for many gastroesophageal diseases, risk reduction in or healing of non-steroidal anti-inflammatory drugs-associated ulcer disease and stress ulcer prophylaxis in intensive care unit patients. Thus PPIs account for a significant proportion of pharmaceutical health-care expenditure. Much of this high expenditure results from overuse of PPIs in account of inappropriate indications or prolongation of therapies for excessive time compared to real need. PPIs overutilization occurs in all medical care settings: in the majority of hospitalized patients with low risks for gastrointestinal bleeding, in patients healed at discharge from hospital, in outpatients in ambulatory practice. However potential adverse effects associated with PPIs therapy have been described, including enteric (especially by Clostridium difficile in elderly patients) and pneumonia infections, nutritional deficiencies, rebound acid hypersecretion, acute interstitial nephritis, gastric neoplasms, bone fractures. Caution is required for some coprescription, particularly with clopidogrel.