Summary. We study 2-knots with virtually solvable group by applying recent work of Freedman to the 4-manifolds obtained by surgery on such knots. In particular we show that "Gluck reconstruction" is the only ambiguity in recovering the Cappell-Shaneson knots (as TOP locally flat knots) from their groups alone.In [18] Gluck showed that if K is a 2-knot then there is at most one other knot with homeomorphic exterior. The optimistic expectation that the exterior might determine the knot was confounded by Cappell and Shaneson [-6] and Gordon [19]. Here we shall show that nevertheless the 2-knots of Cappell and Shaneson are determined as TOP locally flat knots (up to Gluck reconstruction and change of orientation) by information which is apparently much weaker, namely by their groups alone. Similarly any 2-knot whose group is torsion free and virtually poly-Tl is determined thus by its group together with the conjugacy class of a normal generator (information which is redundant when the group is metabelian). This would also be so for Gordon's examples if certain standard conjectures hold for their groups.
Our argument begins with the observation that the closed 4-manifold M(K)obtained by surgery on such a knot is aspherical (unless the group is Z, in which case the knot must be trivial). The result then follows easily from the work of Freedman on 4-dimensional surgery and s-cobordism theorems over virtually solvable fundamental groups [16] and that of Farrell and Hsiang on the topological rigidity of almost flat manifolds [13].In [22] we showed that if a 2-knot group rc is virtually solvable and has a nontrivial torsion free abelian normal subgroup then it is either torsion free and virtually poty-Z or has finite commutator subgroup ~z' or is the group with presentation (a, t[ ta =a 2 t). Freedman's work applies to the latter cases also. If re' is finite then the homotopy type of M(K) is determined by rc and a k-invariant in Z/]r([ 7Z; the difficulties in classifying such knots lie in determining Whitehead torsions, the Wall group L~(r 0 and its action on the structure set of M(K). When n' is odd cyclic some computations are feasible, and we