  We review exact results in N=2 supersymmetric gauge theories defined on S^4
and its deformation. We first summarize the construction of rigid SUSY theories
on curved backgrounds based on off-shell supergravity, then explain how to
apply localization principle to supersymmetric path integrals. Closed formulae
for partition function as well as expectation values of non-local BPS
observables are presented.
