  We explore the behavior of the ac admittance of superconductor-normal
metal-superconductor (SNS) junctions as the phase difference of the order
parameters between the superconductors is varied. We find three characteristic
regimes, defined by comparing the driving frequency $\omega$ to the inelastic
scattering rate $\Gamma$ and the Thouless energy $E_T$ of the junction
(typically $\hbar\Gamma \ll E_T$). Only in the first regime $\omega \ll \Gamma$
the usual picture of the kinetic inductance holds. We show that the ac
admittance can be used to directly access some of the characteristic quantities
of the SNS junctions, in particular the phase dependent energy minigap and the
typically phase dependent inelastic scattering rate. Our results partially
explain the recent measurements of the linear response properties of SNS
Superconducting Quantum Interference Devices (SQUIDs) and predict a number of
new effects.
