A series of hexahydrobenzo[3,4]cyclohept[1,2-b][1,4]oxazines, with different substituents at the benzene and oxazine rings and nitrogen atom, was synthetized. The diastereomers and enantiomers of the unsubstituted compound and the related derivatives hexahydrobenzo[5,6] and exahydrobenzo[6,7]cyclohept[1,2-b][1,4]oxazine, hexahydro[1]benzoxepine and hexahydro[1]benzothiepin[5,4-b][1,4]oxazine, octahydrobenzo[3,4]cyclohept[1,2-b][1,4]diazine were also prepared. Some of these compounds inhibited at low doses gastric secretion in pylorus-ligated rats and antagonized ulcers in pylorus-ligated rats plus acetylsalicylic acid and in cold+restraint-stressed rats. When the most active compounds were tested on cats with Heidenhain pouch, they induced unwanted side effects that ruled out further development of these chemical series.