Background Ships and offshore installations are the most common sources of more than 500,000 tons of oil spilled into the marine environment every year. The 1992 Convention for the Protection of the Marine Environment of the Northeast Atlantic (the OSPAR Convention) defined "Special Areas" with tough emission limits as regards oil pollution. Airborne Surveillance Systems are presently used to control outlets of oil, however the technology is too expensive to be utilised efficiently against offshore installations due to their high number. The lack of efficient surveillance methods for offshore installations has meant that so far they have not been included in the strict rules governing oil pollution in the “Special Areas”. In the late 1990s, the OSPAR Commission, (including representatives of the European Commission and of heads of state for 12 Member States plus Iceland and Switzerland] called for technologies, such as OSIS (oil spill indentification system) to be developed so that they could enforce a new type of regulation in these "Special Areas". Objectives The objective of the OSIS (Oil Spill Identification System) project was to demonstrate the viability of a permanently mounted sensor system for identifying oil discharges from offshore installations within North-Sea areas designated as “Special Areas” by the International Maritime Organisation. The OSIS concept was to demonstrate a potential solution to a widespread problem of international concern by developing online remote monitoring of offshore installations in any location, based on new sensor technology, the new generation of communication satellites and the ongoing developments in the Internet. It was to demonstrate the technology required for the implementation and enforcement of programmes or measures adopted under the OSPAR strategy and would provide a tool required to implement Community environment policy and legislation concerning the naval environment, as specifically stated in Danish national regulations from 1998. Results The OSIS project has successfully developed an oil spill sensor providing 'round-the-clock' online surveillance, which has been tested and installed on fixed offshore installations, mainly oil rigs. Over a three-year period, numerous tests were conducted including missions with the Danish Environmental survey ship, as well with German and Dutch oil combat services in the North Sea. The OSIS sensor is able to identify oil-film from a thickness of 0.02 to 2 mm on the water surface. It can estimate the leaked volumes with +-20 % accuracy in normal weather conditions and with some +-40 % accuracy on rough seas. The extension of the leak can be monitored within the distance of 1-1,5 kilometres from the sensor. The data can then be transferred via satellite to onshore decision-makers. Furthermore, the oil spill data is combined with the geographical Information System (GIS), which enables identification of the context of the leak and planning of the corrective actions. The system which has been developed is very inexpensive compared to the usual aerial surveys and much more accurate than a satellite image based system. A new LIFE-ENV co-funded project: “Oil Spill Identification System for Marine Transport” (LIFE04 ENV/DK/000076) launched in 2004, by the same beneficiary, is adapting the sensor and transmission OSIS system to make it suitable for ships. This project has been awarded the title of "Best of the Best" from a shortlist of 21 "Best" LIFE Environment projects in 2005-2006