This paper presents the petroleum concentration in the Vistula River measured in Tczew from the end of 2007 to October 2012. The most polluted water was after an oil spill, when the oil concentration exceeded 500 μg/kg. Most of the results ranged from 2 μg/kg to over 100 μg/kg and the mean concentration was 54 μg/kg. Petroleum content in the river appeared to be of seasonal variability. The oil concentrations were lowest in summer, while winter was the season when the water was most polluted with oil. The petroleum pollution of the Vistula corresponded to the general condition of its water quality expressed by the BOD₅. The annual input of petroleum to the Baltic Sea amounted to over 1,200 tons.