Neutralino searches at the LHC and dark matter

Supersymmetric models with R-parity conservation provide an excellent candidate for Dark Matter, the Lightest Supersymmetric Particle. There are several possibilities for the Lightest Supersymmetric Particle, we will focus on the lightest neutralino. We will present the ATLAS discovery potential for Supersimmetry with the first $fb^{-1}$ of ATLAS data, and techniques we plan to use for reconstructing decays of SUSY particles at the LHC. We further discuss how such measurements can be used to constrain the underlying Supersymmetric model and hence to extract information about the nature of Dark Matter.