Objectives The North Sea is one of the most productive ecosystems in the marine environment, but significant input of toxicants from very diverse sources occurs, which may harm this ecosystem. Up till now little attention has been paid to sea-based sources of pollutions (e.g. accidental spills or leakage from platforms). Although most of the public interest has gone to oil spills and the quantity of chemicals transported is substantially less than oil, the potential harm for the marine environment from a given amount of chemicals spilled can be several orders of magnitude greater. Many of the chemicals transported by sea are highly toxic and/or persistent, can bioaccumulate or cause long-term effects. In case of an accident at sea, it is important that accurate information on environmental partitioning, bioavailability, (eco)toxicity is immediately available. A number of databases on physical and chemical properties of chemicals have already been developed, but little attention has been paid to specific issues such as the impact on marine live, environmental fate, bioaccumulation in marine food chains. Most often the interpretation is left to the expert user of the database. This project aims at developing a database, amendable for interpretation, providing reliable, easy to interpret and up-to-date information on marine specific issues. The most important parts will be the direct and indirect effects on marine biota and the data quality assessment. Methodology The project can be divided in 4 distinct phases. In the first phase, 400 priority contaminants will be listed to be included in the database. Selection will be performed based on criteria such as bioaccumulation potential, toxicity, persistence, frequency of involvement in accidental spills, frequency of transport over sea and volumes transported. This list will be compared with other existing priority lists. In the second phase an extensive literature search will be performed to gather all information necessary for the database. In the third phase quality and relevance of the gathered data will be assessed. The data will be classified based on the availability of the following information: performance of the tests according to internationally accepted procedures, information on the ëcontrolí, information on the test concentration range, availability of information on test characteristics, statistical analysis and analytic performance. Only relevant data that meet high quality standards will be used in the database. Procedures for risk management will also be included. The most important part will be the sub-module on effects for the marine environment. A broad range of organisms and endpoints will be assessed, but if no data for the marine environment are available, results from freshwater studies will be used. Further, biodegradation, metabolism, detoxification and bioaccumulation will be considered. In the fourth phase the relational database with a graphical user interface will be developed.