Alkylamino-propanol derivatives of 3-alkyl-5-(2-hydroxystyryl)-isoxazole, of the general formula ##STR1## where R is hydrogen, alkyl of 1 to 8 carbon atoms, which is unsubstituted or substituted by hydroxyl, alkoxy of 1 to 3 carbon atoms or cycloalkyl with 3 to 8 carbon atoms in the ring, alkenyl or alkynyl of 2 to 8 carbon atoms, or cycloalkyl with 3 to 8 carbon atoms in the ring, the cycloalkyl rings being unsubstituted or mono- or di-substituted by alkyl of 1 to 3 carbon atoms, and R' is alkyl of 1 to 4 carbon atoms, and their addition salts with physiologically acceptable acids, their preparation, and pharmaceutical formulations which contain these compounds and which can be used as valuable drugs in the treatment of hypertonia, coronary diseases of the heart and cardiac arrhythmias.