Let A and B be
commutative rings with identity, let X be an indeterminate over A and B, and let
A[[X]] and B[[X]] be the formal power series rings over A and B, respectively. The
motivation for this paper was to consider the analogue of a question raised by
Coleman and Enochs for the polynomial ring. Specifically, the following
question is considered: (∗) If A[[X]]≅B[[X]], must A≅B? (The author knows no
counterexample.)