If the particle that makes up cosmic dark matter is a weakly-interacting massive particle, it should be
produced in reactions at the next generation of particle accelerators. Measurements at these accelerators can
then be used to determine the properties of the dark matter particle. From these, we can predict the cosmic
density of the particle, its annihilation cross sections, and the cross sections relevant to particle detection. I
will describe studies done in supersymmetry models with neutralino dark matter that give quantitative
estimates of the accuracy to which these quantities can be determined from measurements expected at the
LHC proton-proton collider and at the ILC electron-positron collider. These studies illustrate how collider data
can be used in conjunction with dark matter detection experiments to understand the nature of dark matter.