This study aim was to evaluate the resource consumption and costs related to gastrointestinal adverse events of non steroidal anti-inflammatory drugs (NSAIDs) from the perspective of the Italian National Health Service. A retrospective, observational study of 3–6 months’ duration. 51 General Practitioners (GPs) in Italy. Participating GPs were asked to fill up, for at least a three months’ period, a report form describing adverse events in pts. with ostheoarthritis and rheumathoid arthritis treated with NSAIDs. 541 adverse events of different severity were recorded. Costs related to one day therapy per event were the following: 1,54 € for gastro-intestinal event (dyspepsia and abdominal pain), 2,41 € for bleeding without hospitalisation, 21,71 € for bleeding with hospitalisation, 2,73 € for ulcer without hospitalisation, 14,06 € for ulcer with hospitalisation, 60,05 € for ulcer complications. Within each category, costs were higher for hospitalised pts. compared with outpatients. When only non-hospitalised pts. were considered, there were wide cost differences among the four categories of adverse events. Treatment costs due to each adverse event related to NSAIDs are relevant. Hospitalisation is the major driver of cost (more than 78% of the total cost); when hospitalisation is not required, the major driver of cost is drug prescription (more than 52%).