This paper is aimed at analyzing the criteria used by credit rating agencies to assign different credit ratings and at evaluating the factors that restrain Peru from obtaining an investment grade. Typically, the sovereign rating expresses an opinion, based on both quantitative (macroeconomic indicators) and qualitative indicators (political and institutional risks), about a government's disposition and ability to duly repay all of its financial obligations. Several agencies coincide in rating some countries with an investment grade rating. While S&P and Fitch are stricter than Moody´s in rating countries with an investment grade, Moody's is stricter with countries rated with a speculative grade. In recent years the Peruvian economy has improved significantly and even at a faster pace in terms of growth, inflation and vulnerability ratios than many of Peru's peer-countries. Factors restraining the country from obtaining a better credit rating include the economy's high dependence on commodities, but the low concentration of exports and their relatively higher "diversification" are not taken into account. As regards the external debt, although the weight of the debt is still significant, important efforts have been made to reduce it. Together with the expansion of the tax base and a better management of government spending, this will contribute to improve fiscal flexibility. Another factor considered is the high level of dollarization in the economy. The best way to reduce it is through the persistence of low levels of inflation, an aspect in which Peru is performing even better than economies rated with an investment grade. Along with its significant level of NIRs, the country's low levels of inflation constitute the best coverage against this risk. In order to overcome some of the institutional deficiencies and political limitations, the government should promote a reform in the system of law and justice, gradually reduce the informal sector, and strengthen institutions and the political levels of government. This important progress in macroeconomic terms has been more extendedly recognized by Fitch and S&P, and contrasts widely with Moody's maintaining the rating assigned to Peru. It seems quite evident that Moody's decision is based on the high weight attributed to the Peruvian debt in foreign currency and the degree of dollarization in the economy, rather than on the favorable evolution of macroeconomic indicators, such as the highly significant accumulation of international reserves, which is an indicator of improvement that cannot be denied.