We investigated a hydrostatic equilibrium model of the Milky Way following Parker (1966), to constrain the large scale properties of the interstellar medium. In our approach we found an excellent agreement between our simple hydrostatic equilibrium model of the Milky Way and the recent all-sky survey data rangeing from the gamma-ray to the radio regime. On large scales the galactic disk-halo system is found to be stable against Parker-instabilities. Pressure support from the Galactic disk is essential to stabilise the halo. In particular the diffuse ionised gas layer acts as a disk-halo interface. Assuming that the distribution of the soft X-ray emitting plasma traces the gravitational potential, we derived the dark matter content of the Milky Way to be about M ~ 2.8 10^11 M_o. Our findings are consistent with the rotation curve of the Galaxy.

6 pages, 5 figures, to be published in the Proceedings of "The Third Stromlo Symposium: The Galactic Halo"