BACKGROUND: Use of nonsteroidal antiinflammatory drugs (NSAIDs) is a well-known cause of gastrointestinal (GI) adverse events. To protect patients at risk, several strategies are advised, including concomitant treatment with proton-pump inhibitorsr switching to cyclooxygenase (COX)-2 selective NSAIDs. It is as yet unknown how many patients at risk for NSAID-induced events are protected. OBJECTIVE: To estimate the number of patients using GI preventive treatment while at risk for NSAID-induced GIevents. METHODS: Records of patients using NSAIDs consecutively for at least 100 days (from 2001 to 2002) were obtained from the PHARMO system in the Netherlands (N = 1,000,000). GI preventive treatments were classified as adequate or inadequate based onevidence-based criteria. Adequate treatment was defined as concomitant use of misoprostol (>400 microg daily), histamine2-antagonists (> or =2 times recommended dose) or proton-pump inhibitors (> or =1 recommended dose), or alternative treatment with COX-2 selective inhibitors. RESULTS: A total of 10,121 patients met the study inclusion criteria; 70% were women. One or more preventive strategies were prescribed in 4340 patients (42.9%), of which 2799 (64.5%) were adequate and 1541 (35.5%) inadequate. Prescribing of adequate preventive treatments increased with the number of risk factors, from 13.3% among those with no additional risk factors to 61.9% for those with > or =4 risk factors. CONCLUSIONS: Although risk factors for GI damage were recognized,a large number of patients in the Netherlands were not or were inadequately protected against potential NSAID-associated GI damage. Despite recommendations, and even in the presence of > or =4 risk factors, almost 40% of these patients were not prescribed adequate GI preventive treatment.