This paper gives a necessary
and sufficient condition that certain topological algebras A (normed algebras and
algebras which are inner product spaces) be left (right) annihilator algebras. It is
assumed that the socle of A is dense in A and that a proper involution ∗is defined on
the socle. Then the necessary and sufficient condition is essentially that the minimal
left (right) ideals of A be complete in the norm on A and be a Hilbert space in an
equivalent norm.