Many-sorted algebras are used in Computer Science for abstract data type specifications. It is widely believed that many-sorted algebras are the appropriate mathematical tools to explain what abstract data types are ([1]). In this paper we want to extend the concept of a hypersubstitution from the one-sorted to the many-sorted case. Hypersubstitutions are used for one-sorted algebras to define hyperidentities and M-solid varieties ([2]). We will prove that extensions of hypersubstitutions for many-sorted algebras are endomorphisms of the many-sorted clone of a given type. As in the one-sorted case we define a binary operation for hypersubstitutions and prove that with respect to this operation all many-sorted hypersubstitutions form a monoid.
