To clarify the pathogenetic mechanisms in acute gastric lesions induced by vibration (VIB), the effects of VIB (3.0 G, 10 Hz, 90 min) on changes in gastric mucosal blood flow (GMBF), plasma corticosterone (COR) and catecholamines (CA) as well as ulcer formation were compared with those of forced water immersion stress (FWI). While the VIB increased the GMBF during the exposure, the FWI decreased it during and after the stress. No difference in the severity of ulcer formation between the VIB groups was seen. Although both VIB and FWI increased the COR and CA, the degree of increased in the COR by the VIB tended to be less than that by the FWI. The truncal vagotomy inhibited the reduction of the GMBF and ulcer formation by the FWI, but promoted the reduction of the GMBF by the VIB. These results suggest that ulceration induced by VIB is caused primarily by its direct, mechanical and specific actions and not through the central nerve system.