Gastrointestinal symptoms and lesions are often associated with the clinical use of non-steroidal antiinflammatory drugs (NSAIDs). An open-label, single arm multicenter Italian study evaluated if misoprostol, a prostaglandin E1 analogue with gastroduodenal mucosal protective activity, was effective in the prevention and treatment of NSAID-induced gastroduodenal lesions. Patients affected by rheumatoid arthritis (RA) or osteoarthritis (OA), in treatment with NSAIDs and suffering from gastric symptoms or gastroduodenal lesions related to NSAID use, were admitted to the study. Gastrointestinal and arthritic symptoms were assessed before and after 4 weeks co-administration of an NSAID (the most frequent was diclofenac, used in 35% of the RA and in 22% of the OA patients, followed by piroxicam and tenoxicam respectively) + misoprostol (200 mcg two times daily in 58% of the cases, 200 mcg three times daily in 39%, 200 mcg four times daily in 3%). On admission and after 4 weeks of therapy a gastrointestinal endoscopy was performed to evaluate the condition of the gastroduodenal mucosa. Final results showed that: (i) NSAID-related gastric lesions were more frequent than duodenal lesions; (ii) when patients were given misoprostol and NSAIDs, 96% of them did not develop gastric lesions and 97% did not develop duodenal lesions; (iii) even when NSAID therapy was continued, gastric or duodenal lesions induced by NSAIDs healed or in any case did not worsen in 92% and 91% respectively of the cases; (iv) during the period of coadministration of NSAIDs+misoprostol, NSAID-related UGI symptoms disappeared or improved in 77% of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)