I present a large catalogue of 502,705 close halo pairs extracted from the Millennium Simulation. Using a simple five-stage scenario, I perform statistical analyses of the halo pairs and their evolution. Separations, redshifts,total masses, mass ratios and relevant lifetimes are investigated. This catalogue will play a fundamental role in forthcoming studies focused on the early stages of galaxy mergers, interaction-induced star formation, binary (and multiple) quasars, and setting up the initial conditions for black-hole coalescence.