Key outstanding questions regarding dark matter are formulated, as a backdrop to the upcoming discussions at this meeting. A major issue involves how many species of dark matter there are, and whether both baryons and non-baryons are implicated in cosmological dark matter. How is dark matter distributed relative to baryons on all scales? Are voids really empty? And finally, is there high-amplitude structure in the matter distribution of the universe on scales ∼100 Mpc, and, if so, how can it be accounted for in terms of known, plausible physical processes?