In previous nerve tracing studies we found evidence that the efferent gastric vagus nerves supplying the anterior gastric wall had a regional organization. The first part of this study aimed to determine whether vagus afferent nerve cells supplying the stomach have a regional organization; an ipsilateral pattern of innervation was found. Next, selective blockade of the afferent nerves was performed and verified by axonal tracing. Animals with afferent blockade were stressed to determine the effect of afferent nerve blockade on the gastric stress response. After selective blockade of afferent vagus nerves to the anterior gastric wall in rats, water-immersion stress was then applied. The part of the gastric wall with afferent nerve blockade had fewer acute gastric lesions than control animals or the contralateral side of the stomach after 24 hr of stress. This study supports the hypothesis that afferent as well as efferent vagus nerves have an ipsilateral arrangement. Afferent nerve blockade of the left vagus nerve protected the anterior wall of the stomach against stress ulceration.