The X-ray absorption spectra of AGNs

X-ray absorption provides important clues to the origins of the gas flows in active galaxies and quasars (AGN). Both observational and theoretical evidence suggests that a large fraction of the gas in these objects is highly ionized, and therefore best observed in X-rays. Current X-ray spectral observations constrain the degree of ionization of this gas. I will present a summary of these results, together with a discussion of models for the spectra and predictions for future observations.