In master thesis researches to appreciate the agrarian strain to basin of river Tatula in the North karst region area of Lithuania. Object of the work: The basin of river Tatula, which is in the North karst region area of Lithuania. Aim of work: 1. gather up the water samples of river Tatula in autumn and spring; 2. to do ourselves the water quality researches of river Tatula; 3. to collect farmers in basin of river Tatula by questionnaires method; 4. to sum up the results and to dimension pollution’s sizes and sources; Methods of the work: The river samples were taken in 2003, 2004 autumn and 2004, 2005 spring. Water samples were taken up to the river, middle of the river and down to the river. Then water samples were transported to a laboratory, where would be setted: pH of the water, permanganate oxidation, BDS, ammonium azote concentration, phosphate phosphorus. Also were collected farmers who were farming in basin of Tatula by questionnaires method. Work out results of the waters quality shows that agrarian work effect partially influence pollution basin of river Tatula. When were done water‘s researches of river Tatula were setted ammonium azote concentration exceeded DLK and river water's quality was bad, compare with the other assay parameters water‘s quality is unbroken DLK. Keywords: The North karst region area of Lithuania, the basin of river, the agrarian strain, BDS7, pH, ammonium azote.