The main pollution sources of the Siret river and its tributaries in the Bacau-Marasesti span are submitted in the present study. The Siret River, through the watershed it forms, is one of the largest tributaries of the Danube. Thereby Siret river through its water volume outlet for the Danube River, which crosses our country, is considered a major pollution agent for the surrounding areas of the river from a social, economical and agricultural point of view.