Cosmology using the Parkes Multibeam Southern-Sky HI Survey

I discuss the implications of the Parkes HI Multibeam Southern Sky Survey for cosmology. It will determine the local mass function of HI clouds, detecting several hundred per decade of mass. Each of these will come with a redshift and, for the more massive clouds, an estimate of the velocity width. This will provide an ideal database for peculiar motion studies and for measurements of biasing of galaxies relative to the underlying matter distribution.