It follows from Culler, Gordon,
Luecke and Shalen’s Cyclic Surgery Theorem that any knot complement is covered
by at most two knot complements. Gonzales-Acuna and Whitten proved a result on
the other direction: A given knot complement can cover at most finitely many knot
complements. This paper is to show that the best possible result in this direction
holds: A given knot complement can nontrivially cover at most one knot complement.
Moreover, if the knot is not a torus knot, then the covering map is unique up to
equivalence.