In the year 2012 the risk premium of government bonds of European countries partly increased to dizzying height. This was caused by the increasing debt problem of the European economic area and was especially related to the PIIGS countries. Due to contagion effect from Greece, Portugal, and Irland, the lacking credit worthiness of Spain and Italy come to the fore. The fear of a country?s insolvency and the connected national bankruptcy have risen since then. The bankruptcy of a country is attended by a default of a government bond. The credit spreads and credit default swaps of a government bond are two market barometers to determine the default probability and default risk of a government bond. Furthermore, you need a recovery rate to determine the default probability that indicates the rate of receivables in the case of insolvency. The creditors obtain this rate despite bankruptcy. The default probability could be determined through two model-theoretical approaches. These two models are the structural models and the reduced form models. Both models are acting on the assumption of a risk-neutral investor, although the reality is different. The solution of this problem is the transformation of the risk-neutral default probabilities to risk-averse probabilities. The following master thesis covers the different calculation opportunities of the implicit default probability in a risk-neutral and risk-averse model on the basis of credit spreads and credit default swaps of government bonds. In addition it covers the fundamental parameter of the loss given default, recovery rate and other different factors of influence.