Recent years have seen an increase in the exploitation of hydrocarbon resources in the subsoil of the territorial sea and continental shelves of coastal states. Where a hydrocarbon reservoir is discovered which traverses the delimited or disputed maritime boundary of two or more coastal states it is required to be developed jointly according to the principles of international law. While an international legal regime in respect of unitization or joint development is not set out in statute, international treaties and principles guide the process. This work examines the international legal principles relating to the rights and obligations of coastal states in the territorial sea, continental shelf and exclusive economic zone and considers joint development arrangements in delimited as well as disputed maritime boundaries. Key issues of the negotiating process are addressed. It explores the ongoing Trinidad and Tobago /Venezuela unitization process. A relatively new phenomenon in the oil and gas industry, only eight unitization/joint development agreements have been concluded to date.