  We present a Monte Carlo method to simulate asymmetric binary mixtures in the
grand canonical ensemble. The method is used to study the colloid-polymer model
of Asakura and Oosawa. We determine the phase diagram of the fluid-fluid
unmixing transition and the interfacial tension, both at high polymer density
and close to the critical point. We also present density profiles in the
two-phase region. The results are compared to predictions of a recent density
functional theory.
