Terminalia avicennioides is used commonly in Nigeria and other countries worldwide in traditional medicine for the treatment of various ailments including gastroduodenal ulcers. The dark-brown methanol extract obtained from the bark of the plant was tested to determine its antisecretory gastric acid activities using rats. The extract at the dose rates of 350, 420, and 504 mg/kg, inhibited significantly (P Ͻ 0.05) gastric acid secretion in normal rats. The extract at the highest dose (504 mg/kg) used also significantly (P Ͻ 0.05) inhibited gastric acid secretion in rats pre-treated with histamine, which may indicate that the extract inhibits HCl secretion by interacting with H 2 -receptors. This finding undoubtedly validates the folkloric use of T. avicennioides in the control of gastroduodenal ulcers.