Even if dark matter particles were unambiguously discovered in experiments, there is no clear reason to expect that this would resolve the dark matter problem. It is very easy to provide examples of dark matter scenarios (e.g. in supersymmetric models) in which nearly identical detector signals correspond to extremely different relic densities. The density of the discovered particles, therefore, must be determined before their cosmological relevance can be established. In this paper, I present a general method that utilizes both dark matter and hadron collider experimental data (once they become available) to estimate the local density of dark matter particles. These results were obtained in collaboration with Gordon Kane at the University of Michigan.