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The observed properties of the multiple gas phases comprising the Milky Way halo will be reviewed. The emphasis will be on properties inferred from ultraviolet absorption line studies performed with the HST toward Galactic O and B stars and toward bright AGN's and quasars. These new measurements provide information about the Galactic scale heights of the different gas phases, the gas phase elemental abundances in halo clouds, and the physical conditions in the gas. The extragalactic observations reveal information about Galactic H I high velocity clouds (H I HVCs) and about gas in the outer Milky Way. Elemental abundances have been measured for several H I HVCs and a new class of highly ionized Galactic HVCs has been discovered. Absorption by C IV is found at large Galactocentric distances ($>$ 25 kpc) in the outer warped region of the Milky Way.
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