The secondary gastrointestinal effects associated with the use of non-steroidal anti-inflammatory drugs (NSAIDs) are well documented in the medical literature. Less addressed is the 'iatrogenic' cost due to the treatment of these secondary effects. Epidemiologic and clinical studies report that the cost of NSAIDs is multiplied by a coefficient that ranges from 1.45 to 3, if the cost of treating the induced gastrointestinal complications is considered. A simple methodology incorporating the direct medical cost of treating complications has been developed to calculate a 'shadow price' of an NSAID, thus reflecting the real cost to the payer of NSAID therapy. The model has been used to compare three NSAIDs on the basis of their relative prices and gastroduodenal toxicity.