NEW MATERIAL:The 1,5-benzothiazepin-4(5H)-one derivative of formula I (R1 is H, halogen, lower alkyl or lower alkoxy; R2 is benzoyl, substituted benzoyl, or halogen- or lower alkoxy-substituted phenylsulfonyl; R3 is lower alkylaminoalkyl) or its acid addition salt.

EXAMPLE: 2-(4-Methoxyphenyl)- 3-(2,5-dichlorobenzenesulfonyloxy)-5-(2-dimethyl aminoethyl)-1,5-benzothiazepin-4(5H)-one.

USE: A medicinal drug having pharmacological activities such as calcium antagonistic, central nervous controlling, coronary vasodilating, antiarrhythmic, local anesthetic, analgesic, antiinflammatory, and diuretic activities. It has low toxicity.

PREPARATION: The compound of formula I can be prepared by reacting the compound of formula II or its acid addition salt with a halogen reagent.