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OIL RESERCHES ON THE SOUTHERN BALTIC AREA AND PROTECTION OF NATURAL ENVIRONMENT Summary The paper deals with prospects of search for hydrocarbons in the South Baltic Sea and measures taken against possibility of natural environment pollution. Up to date, on the East European Platform, the best results have been achieved in the Soviet Baltic Republics where 25 oil deposits have been discovered. The main productive horizons belong to Middle Cambrian, only few are of Ordovician origin and none has been found neither in the Silurian nor in the Upper Palaeozoic and Mesozoic which are considered non productive. The are few small oil deposits discovered in Gotland, and a Middle Cambrian oil deposit of Dembki – Żarnowiec located in the Łeba (Uplift) in Poland. On the Epicaledonian Central European Platform, there are many onshore oil and gas deposits in Poland, GDR and FRG. The gas deposits were discovered in Lower and Upper Carboniferous and Rotliegendes when oil deposits were found in Zechstein Main Dolomite. Since 1975 "Petrobaltic" has been searching for oil and gas in the Polish, GDR and Soviet sectors of the Baltic Sea. The search resulted in discoveries of a few oil and gas deposits in the Middle Cambrian sediments. The reserves of those deposits are estimated as over 20 million tons. There is no success yet in searching for oil and gas in the western part of the Baltic Sea on the Epicaledonian Platform. According to the recent seismic and geologic results, the majority of prospective structures in the Baltic Sea is explored already, and in Author's opinion, the remaining ones are of similar or even inferior quality. Therefore, before the next step of exploration will be taken, it is necessary to comprehensive analysis of all economic, geologic and naturalistic factors. According to the resolution of the International Convention held in Helsinki (1974), the natural environment of the Baltic Sea should be strictly protected by all Baltic States. This resolution imposes compulsory ventures to the offshore exploration, especially against possibility of sea, bottom and shore pollution when drilling and testing wells on discovered deposits. The regulations valid for the offshore exploration are met by construction of the "Petrobaltic" drilling platform. The well is protected by cemented pipe columns with special high pressure valves and anti-explosion preventers; mud circulation and wastes are hermetically closed in special system consisting of pipes, filters, separators and tanks. Those devices despite of its high quality, do not exclude the possibility of uncontrolled eruption and spilling of oil and gas. This was the reason why the Soviet Union government in 1986 gave up the exploitation of offshore oil deposit discovered near Kuronian Sand-Bar with its unique Natural Park.