SUMMARY1. Anti‐ulcer and sedative effects of tranquillosedatives viz. benzodiazepines (diazepam, oxazepam and nitrazepam), barbiturate (phenobarbitone), phenothiazines (chlorpromazine, trifluoperazine and thioridazine) and butyrophenone (haloperidol) were compared in albino rats.2. Ulceration of the glandular stomach was induced by 2 h restraint at 4°C. Sedation was measured using the rotarod test.3. These tranquillosedatives showed dose dependent anti‐ulcer and sedative effects. The relative potency and therapeutic index (ratio between rotarod ED50and anti‐ulcer ED50) of each drug were determined. Diazepam showed the highest therapeutic index (1.88).4. Diazepam significantly reduced the volume of gastric secretion, raised its pH and prevented the gastric ulcer formation in pylorus ligated rats but failed to prevent the acute duodenal ulceration induced by intramuscular injection of histamine or carbachol in guinea‐pigs and rats, respectively.5. These observations suggest that benzodiazepines (diazepam) are more suitable anti‐ulcer agents compared to barbiturate, phenothiazines and butyrophenone. The anti‐ulcer effect of diazepam is possibly due to a combination of sedative, anti‐anxiety and antisec