Bachelor Thesis from the year 2009 in the subject Business economics - Banking, Stock Exchanges, Insurance, Accounting, grade: 1,0, University of Applied Sciences Fulda, language: English, abstract: In the beginning of 2008 the word "Subprime" was elected by brokers, analysts and traders at the stock market Frankfurt for the "Unwort 2007". Whereat "Subprime" just means that something is just below (sub) of top quality (prime). The choice was constituted by the fact that the translation belittles this word and deceptively describes the true quality of Subprime real estate loans. The following bachelor thesis analyzes and intends to look into the reasons for the Subprime Crisis, which burst out in the beginning of 2007 and at the time of this writing - November 2008 - continues to seriously affect the global economy. This thesis is structured in various chapters. First and before beginning the analysis of the crisis, chapter 2 will introduce mortgage backed securities (MBS), the financial instruments that were used to securitize the subprime loans. Thereafter chapter 3 describes the rating of these MBS, based on which chapter 4 analyses the reasons of the Subprime crisis and explains that not merely one single factor caused the crisis, but rather an interaction of different factors and a progression of several years created this crisis which already had and will have far reaching consequences for all parts of the world and the economy.