Abstract: This specification concerns the use to treat hypertension in mammals of novel and known 4H-s-triazolo[4,3-a][1,4]benzodiazepines, known 4H-s-triazolo[4,3-a][1,3,4]benzotriazepines and 2,4-dihydro-2-alkyl-1H-s-triazolo[4,3-a][1,4]benzodiazepin-1-ones, and novel 2,4-dihydro-2-alkyl-1H-s-triazolo[4,3-a][1,4]benzodiazepin-1-thiones.