Underlying Event Simulation in the Herwig++ Event Generator

We study Quantum Chromodynamics (QCD) at hadron colliders. This is done in the context of general purpose Monte Carlo Event Generators. The aim of this thesis is to develop and implement a model for the so--called Underlying Event for the program Herwig++. We discuss multiple parton-parton scattering as source of the UE and show that our implementation is able to describe existing data from the Tevatron collider very well. Nevertheless we extend this model by a soft, non-perturbative component.