In an earlier study, we were able to show that giant fold gastritis is probably a special form of Helicobacter pylori-associated gastritis. Proof of this contention, however--namely regression of the giant folds following eradication of the organism--in a large number of patients was not then possible. To rectify this, Helicobacter pylori (HP) eradication treatment with omeprazole and amoxicillin was applied to 47 patients with HP gastritis and giant folds (5 patients with giant folds localized in the anterior or posterior wall, 42 patients with generalised giant folds within the corpus and fundus). The results of treatment were investigated by endoscopy and histology at the earliest 4 weeks after termination of treatment. In 40 of the 47 patients (85.1%), HP eradication treatment was successful. In 7 patients in whom treatment was unsuccessful, follow-up examinations revealed no changes in the endoscopic or histological findings. In 2 out of 3 patients in whom the endoscopic findings were unchanged despite successful HP eradication, biopsy material revealed the cause of the giant folds to be a signet ring cell carcinoma; in the remaining patient the cause of giant fold persistence was unclear. In 36 patients, the endoscopic--findings normalised completely, while in one patient there was obvious regression of the giant folds. We conclude from this study that giant fold gastritis is indeed a special form of HP gastritis, and that eradicating the organism in patients with gastric giant folds may help to distinguish between inflammatory, hyperplastic and tumorous giant folds.