New thiazolotriazines having the formula ##STR1## (where R.sup.1 is aryl and R.sup.2 is ar(lower)alkyl, lower alkyl or lower alkenyl) and their pharmaceutically acceptable acid addition salts are described. The corresponding thiazolotriazinium compounds comprising a cation having the formula ##STR2## (where R.sup.1 and R.sup.2 are as explained above and R.sup.3 is ar(lower)alkyl, lower alkyl or lower alkenyl) and a pharmaceutically acceptable anion are also described. The compounds are indicated for use as anti-ulcer agents.