We study the determinants of sovereign debt credit ratings using rating notations from the three main international rating agencies, for the period 1995-2005. Using linear methods and ordered response models we employ a new specification that allows us to distinguish between short and long-run effects, on a country's rating, of several macroeconomic and fiscal explanatory variables. The results point to a good performance of the estimated models, across agencies and time, as well as a good overall prediction power. Changes in GDP per capita, GDP growth, government debt, government balance have a short-run impact on a country's credit rating, while government effectiveness, external debt, foreign reserves and default history are important long-run determinants.JEL: C23; C25; E44; F30; G15