General Average is a concept that is peculiar to maritime transport and has its origins in the earliest days of sea-borne trade in the Mediterranean. The basic principle was recognised by sea-faring nations in similar terms: any sacrifice of property, such as jettison, or any extraordinary expenditure that is made for the common safety of ship and cargo is contributed to by the surviving property on the basis of arrived values. In the eighteenth century divergence between English and European/US law and practice in the application of this principle became a serious inconvenience to commercial interests and from 1860 onwards there was a concerted international effort towards greater uniformity, culminating in the York-Antwerp Rules of 1890, which became operative by insertion into contracts of affreightment. This article traces that initial movement for uniformity and outlines subsequent reforms and new controversies that have emerged as the Rules have been revised periodically, including proposals to be considered by the Comite Maritime International in Vancouver between 31 May and 4 June 2004.