Master's Thesis from the year 2013 in the subject Business economics - Business Management, Corporate Governance, grade: 1,7, University of applied sciences Dortmund, language: English, abstract: Mergers& Acquisitions (hereafter collectively referred to as M&A) seems to be an ambivalent issue. On the one hand the worldwide number of M&A deals increased tenfold from 1985 to 2012. On the other hand the failure quote of M&A deals lies between 70 and 90 % according to an article in HBR from 2011 with reference to several studies. Companies in the modern economic environment get increasingly complex and aligned to international activities. The mix of employees gets more and more diverse, people have different values, imaginations and opinions. This initial position makes it increasingly difficult for people to work together. Many conflicts appear in everyday working life. They are frequently not solved and remain subliminal for a long time. Besides that demo-graphic change continuously influences the working world of today. Those developments come up to a much higher shape in M&A deals. One of the main reasons, why M&A deals fail is negligent human resources management (hereafter collectively referred to as HRM). People in power seem to be not informed and skilled sufficiently to handle M&A situations appropriate, as a huge number of M&A deals fail. In numerous cases insufficient attention to HRM with all its problems in this special change situation is responsible for the failure. It is a major challenge for companies and their leaders to solve interpersonal and professional problems within their company that can occur in conjunction with an M&A deal. The challenge for top management and HRM is to be well prepared for all upcoming problems, whether they are interpersonal or professional. In M&A deals huge amounts of money are invested combined with dependencies as jobs, competitiveness and success of a company. Therefore the critical success factor HRM in M&A is worth to be examined closely.