The program COMBI is used to simulate self-consistently the coherent and incoherent beam-beam interactions in the LHC which are the main limitations for its performance. For a realistic simulation it is necessary to treat as many bunches as possible up to the real number of almost 6000 for the two beams together. The particles in a bunch are represented by 1000 to 100000 macro-particles to provide a self-consistent simulation of the underlying physics.