Three hundred and thirty-four pyloric type and 244 fundic type gastric mucosal specimens from 135 patients undergoing upper gastrointestinal endoscopy were checked for Campylobacter-like organisms (CLO) by the Warthin-Starry method. CLOs were found in 77/135 (57 p. 100) patients and in 235/578 (41 p. 100) biopsy specimens. There was no significant difference in the prevalence of CLO-positive specimens in the two types of gastric mucosa. The prevalence of CLO-positive specimens was higher in patients with duodenal ulcer than in the other patients (p less than 0.01). In the whole group, 42 p. 100 of the specimens with gastritis showed CLOs. Neither the type nor the activity of gastritis seemed to be relevant. Twenty-two per cent of the pyloric type and 36 p. 100 of the fundic type specimens classed as normal were positive for CLOs. In the normal fundic type mucosa, CLO-positive specimens were more frequent (p less than 0.01) in those patients with CLO-positive specimens from the antral area than in those without CLOs in the antrum. In 41 patients with multiple specimens from either the duodenal bulb and the stomach, chronic non specific duodenitis appeared to be more frequent in patients with CLO-positive antral specimens. The present study provided data on the frequency of gastric CLOs in a mediterranean population and confirmed that an association between CLOs and antral gastritis exists in patients with duodenal ulceration. However, data of the present investigation indicate that no relation between CLOs and the type and activity of gastritis exists and that CLOs are frequently found in the histologically normal mucosa, particularly in the body-gland area.