We test the theoretical equivalence of credit default swap (CDS) prices and credit spreads derived by Duffie (1999) , finding support for the parity relation as an equilibrium condition. We also find two forms of deviation from parity. First, for three firms, CDS prices are substantially higher than credit spreads for long periods of time, arising from combinations of imperfections in the contract specification of CDSs and measurement errors in computing the credit spread. Second, we find short-lived deviations from parity for all other companies due to a lead for CDS prices over credit spreads in the price discovery process. Copyright 2005 by The American Finance Association.

Wood and seminar participants at the Bank of England and Banco de España for useful comments. Karen Goff and Andrew Paterson provided very able research assistance. CreditTrade and J.P. Morgan Securities kindly allowed us to use their credit default swap data. Numerous people at Banc of America Securities, Bloomberg, BNP Paribas, CreditTrade, Deutsche Bank and J.P. Morgan answered our questions and corrected our misunderstandings. They know who they are and that we are very grateful. BANCO DE ESPAÑA SERVICIO DE ESTUDIOS The Working Paper Series seeks to disseminate original research in economics and finance. All papers have been anonymously refereed. By publishing these papers, the Banco de España aims to contribute to economic analysis and, in particular, to knowledge of the Spanish economy and its international environment. The opinions and analyses in the Working Paper Series are the responsibility of the authors and, therefore, do not necessarily coincide with those of the Banco de España or the Eurosystem. The Banco de España disseminates its main reports and most of its publications via the INTERNET at the following website: http://www.bde.es Reproduction for educational and non-commercial purposes is permitted provided that the source is acknowledged

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