The current worldwide research on air pollution caused by the emission of harmful compounds from ships' engines is based on a simplified input. The existing databases of harmful compound emissions in the exhaust ofvessels operating in various parts of the world cannot be used to estimate emissions in meso- and microscale, e.g. in the Baltic Sea or the Gulf of Gdańsk, because this would lead to excessive generałization of emission factors, mainly due to the lach ofthe reąuired detail concerning vessel motion characteristics. Theflrst issue tackled within the framework ofthe project, one ofwhose effects is to create a research tool in the form of a computer program which simulates toxic compound emissions in the exhaust ofthe main engines ofvessels operating on a speciflc water body, was to create a vessel trafflc database in a selected marinę region (e.g. the Gulf of Gdańsk). The data was obtainedfrom the marinę Automatic Identification System (AIS). In addition to the parameters of vessel trafflc in the analyzed region of the sea, the database created, is a collection ofthe available construction and operat iona! data of those vessels, such as their size, displacement, power rating of the main propulsion engines, etc. Those data, after the appropriate processing, produced the so-called generalized resistance characteristics of the ships which became the basis for the determination of the maximum demand reguired by the screw propeller under given operating conditions. Information of the motive power (inslantaneous) is necessary to determine the emission characteristics of harmful exhaust gases. The extensive research resulted in the development of an original computer program, MEFSAS (Model of Emission From Ships At Sea), which allows to determine the power ratings ofthe screw propulsion engines (and on their basis the emissions characteristics) depending on the aforementioned variables ofthe operating conditions in the static and dynamie, states.