We determine the effective prepotential for N=2 supersymmetric SU(N_c) gauge
theories with an arbitrary number of flavors N_f < 2N_c, from the exact
solution constructed out of spectral curves. The prepotential is the same for
the several models of spectral curves proposed in the literature. It has to all
orders the logarithmic singularities of the one-loop perturbative corrections,
thus confirming the non-renormalization theorems from supersymmetry. In
particular, the renormalized order parameters and their duals have all the
correct monodromy transformations prescribed at weak coupling. We evaluate
explicitly the contributions of one- and two-instanton processes.Comment: 34 pages, Plain TeX, no macros needed, no figure