  BiHermitian geometry, discovered long ago by Gates, Hull and Roceck, is the
most general sigma model target space geometry allowing for (2,2) world sheet
supersymmetry. By using the twisting procedure proposed by Kapustin and Li, we
work out the type A and B topological sigma models for a general biHermtian
target space, we write down the explicit expression of the sigma model's action
and BRST transformations and present a computation of the topological gauge
fermion and the topological action.
