The wave of corporate mergers during the nineties has sparked new interest in economic analyses of the preconditions and consequences of increasing market concentration. Traditionally, static microeconomic models are used to justify threshold levels of market concentration that necessitate policy interventions. This classical approach has recently been complemented by econometric modelling and by simulations based on econometric model specifications.This project will follow both research approaches forwarded so far and will also try to extend the research methodologically. It investigates the following four problem areas:1.) Firm concentration and potential effects of mergers in the German car market.2.) Analysis of competition in the German market for personal computers.3.) Structural modelling and simulation of potential effects of mergers.4.) Analyzing effects of mergers on profits and firm values.