The data on wastewater quality in Kotice region (Slovakia, 240 000 inhabitants) including the biol. O demand (BOD5), the chem. O demand (CODCr), the content of total N, the content of insol. substances (IS), and the content of total P were collected in 2013-2018 and analyzed to det. correlations between the particular indicators. The samples were taken twice a month intervals from the input point of the wastewater treatment facility. The results were presented both graphically and as regression equations.