  In this paper we set up the family Seiberg-Witten theory. It can be applied
to the counting of nodal pseudo-holomorphic curves in a symplectic 4-manifold
(especially a Kahler surface). A new feature in this theory is that the chamber
structure plays a more prominent role. We derive some wall crossing formulas
measuring how the family Seiberg-Witten invariants change from one chamber to
another.
