This book presents the first thoroughgoing analysis of the contractual effect of letters of comfort as it appears in both common law and civil law systems. The commentary draws on cases from a wide variety of jurisdictions and on the full range of legal scholarship on the subject in several languages. Among the specific issues and topics raised along the way are the following: the typology of letters of comfort; the legal nature of letters of comfort; the use of letters of comfort in corporate group and banking practice; the economic explanation for the use of letters of comfort; the contractual effect of letters of comfort in French law; 'ten commandments' of letters of comfort; Clearly evoking the tension between business needs, the law, and judicial application, the book analyses what happens when the relationship between a lender and a creditor breaks down, or the latter becomes insolvent, and courts or arbitrators are asked to determine the legal status of a comfort letter. This is an area of practice in which lawyers in any field of business activity are inevitably concerned, and in which useful guidance is scarce. For this reason this detailed analysis will be very welcome.