This paper examines the circumstances in which a party to an arbitration agreement may be deemed to have waived its right to arbitrate a dispute comprehended by the agreement, by involvement in litigation concerning this dispute. The focus is on the law in common law jurisdictions, particularly Australia and the United States of America. United Kingdom law will also be briefly surveyed. The paper focuses on the 2006 decision of the Australian Federal Court in Comandate Marine Corp v Pan Australia Shipping Pty Ltd, which afforded the topic significant treatment. The theoretical bases for sustaining waiver claims are analysed, including waiver as a discrete doctrine, abandonment, estoppel, election, repudiation of contract and variation of contract. The policies that underlie and inform the development of principles for testing waiver submissions are noted.