  We review the Seiberg-Witten construction of low-energy effective actions and
BPS spectra in SUSY gauge theories and its formulation in terms of integrable
systems. It is also demonstrated how this formulation naturally appears from
the compactified version of the theory with partially broken supersymmetry so
that the integrable structures arise from the relation between bare and quantum
variables and superpotentials of SUSY gauge theories. The Whitham integrable
systems, literally corresponding to the uncompactified theory, are then
restored by averaging over fast variables in the decompactification limit.
