The article presents the analysis of the causes and effects of mortgage credits in the USA. The present credit crisis in the USA and some UE countries is caused by a mechanism of expansion of mortgage banking generating mistaken factors in risk management, mainly as a result of the overvaluation of securities. The crisis in the American subprime market brought about negative effects regarding the liquidity of not only American financial market but the other countries' markets as well. The financial crisis was mainly the result of the excessive expansion of mortgage credits and incorrect assessment of credit risk by rating institutions. Moreover, the American market collapse was caused by the lack of some regulations in the housing market, standards of consumer protection as well as clarity and control of non-banking financial institutions..