  We conjecture an equivalence between the Gromov-Witten theory of 3-folds and
the holomorphic Chern-Simons theory of Donaldson-Thomas. For Calabi-Yau
3-folds, the equivalence is defined by the change of variables, exp(iu)=-q,
where u is the genus parameter of GW theory and q is charge parameter of DT
theory. The conjecture is proven for local Calabi-Yau toric surfaces.
