The anti-ulcerogenic potential of the leaf methanol extract of Ocimum suave (Lamiaceae) was investigated using four methods of gastric lesion induction in experimental Wistar rats (150-200 g): (1) HCl/ethanol-induced gastric lesions, (2) Absolute ethanol-induced gastric lesions, (3) Indomethacin-HCl/ethanol-induced gastric lesions, (4) Pylorus ligation-induced gastric lesions. Administration of the extract of O. suave to the rats by oral route (75-500 mg/kg) dose-dependently prevented the formation of acute gastric lesions induced using the four experimental techniques. The dose-dependent reduction of lesion formation was in all cases accompanied by significant increases in gastric mucus production. At the dose of 250 mg/kg there was complete inhibition of gastric lesions induced using the HCl/ethanol solution. Pre-treatment, by intraperitoneal route, with indomethacin significantly reduced the ability of the extract to inhibit the formation of HCl/ethanol-induced lesions. When the rats were subjected to pylorus ligation, the dose of 500 mg/kg completely inhibited lesion formation but did not have any effect on gastric acid secretion compared with the controls. The mucus secretion promoting effect of the extract was most significant when the gastric environment was highly acidic. These results suggest that a new anti-ulcer therapy regimen may be formulated which does not require the use of antacids and anti-secretory agents.