Traditionally, a reinsurance contract was considered to be an honorable agreement based on mutual trust and confidence between a reinsured company and a reinsurer. However, as the number of reinsurers and reinsured companies has dramatically increased, and the number of claims has significantly risen, the nature and structure of the reinsurance relationship has changed and disputes between reinsurance-contract parties have multiplied accordingly. Reinsurers often insist that they are not obligated to indemnify the cedent companies because these companies have breached their duties, as derived from claims clauses the reinsurance contracts. There have been few reinsurance cases between reinsurers and reinsured companies before Korean courts so far, but, in light of the changing nature of the relationship between reinsurance parties, many relevant future disputes may be resolved by courts instead of by mutual consent. Therefore, it is now useful to examine what claims clauses of reinsurance contract mean; how they interact with other reinsurance clauses or principles, such as follow-the-settlement or follow-the-fortune clauses; and how the breach of claims clauses affects reinsurers’liabilities. Because the legal principles of reinsurance have been developed by English and American scholars and courts, we should carefully examine those countries’reinsurance customs and principles and apply those findings to a reinsurance contract that would be governed by the law of Korea, if possible.