M. Dehn used a
type of homology preserving surgery on S3 to produce an infinite family of
irreducible homology 3-spheres. We apply Dehn’s construction to arbitrary
3-manifolds, give groups invariant under Dehn’s construction, give a reduction
of the Poincaré conjecture, give a nontrivial example of links in S3 with
homeomorphic exteriors, and give a result connerning knots with property
P.