  In this survey we present the interpretation of isomondromy preserving
equations on Riemann surfaces with marked points as reduced Hamiltonian
systems. The upstairs space is the space of smooth connections of GL(N) bundles
with simple poles in the marked points. We discuss relations of these equations
with the Whitham quantization of the Hitchin systems and with the classical
limit of the Knizhnik-Zamolodchikov-Bernard equations. The main example is the
one-parameter family of Painlev\'{e} VI equation and its multicomponent
generalization.
