The aim of this paper is to present the most important theories and selected empirical evidence on the costs of sovereign default. The evaluation of these costs is essential for countries facing a debt crisis for deciding how far they should go to avoid default compared with the costs and benefits resulting from the repayment of their debts. The analysis shows that depending on the selection of econometric model and sample of countries, there are still extreme differences regarding the impact of the sovereign default on economic growth. For example, the costs of not repaying debts can range from zero to 10.5% in the short run while in the medium term it can range from zero to 10%. Similarly, significant differences relate to the impact of sovereign default on the access to the international capital markets and on the size of international trade. The most important potential economic cost of sovereign default inducing governments to repay their debts is its negative impact on the domestic economy through the financial system, mainly banks, which indirectly affects the state of the whole economy. The deterioration of the business environment leads to a reduction in private investments, particularly the investments in human capital, which are very important for the development of modern economies. It leads to the reduction of the efficiency of the economy and GDP growth, and through the operation of automatic stabilizers- -exacerbates fiscal problems (the depth and the duration of the debt crisis). Another important incentive for governments to repay their debts are political costs, which are usually significant and long-lasting. In summary, the results of empirical studies show extreme differences, making it difficult for governments facing a debt crisis to use them to make optimal decisions.