  We construct T-duality on K3 surfaces. The T-duality exchanges a 4-brane R-R
charge and a 0-brane R-R charge. We study the action of the T-duality on the
moduli space of 0-branes located at points of K3 and 4-branes wrapping it. We
apply the construction to F-theory compactified on a Calabi-Yau 4-fold and
study the duality of N=2 SU(N_c) gauge theories in four dimensions. We discuss
the generalization to the N=1 duality scenario.
