A histological study was performed in order to evaluate the prevalence of Campylobacter-like organisms (CLO) and gastric antral lesions in 85 rheumatoid arthritis (RA) patients using NSAIDs, and in 100 nonrheumatoid outpatients comparable in terms of sex and age, not using NSAIDs. Histological evidence of gastritis was a common finding both in RA patients (88.2%) and in nonrheumatoid outpatients (89.0%). On the other hand, CLO were detected in a significantly lower proportion (p less than 0.001) of RA patients than outpatients (30.6 and 59.0%, respectively). Considering each NSAID used separately (aspirin, diclofenac sodium and ketoprofen), no significant difference in the presence of CLO in the three groups was found; in the small group of patients treated with aspirin, however, bacteria were never detected. MICs of each NSAID used against 15 isolates of Campylobacter pylori were also determined.