In this study, water quality of Koprucay River which is one of the most important river in the region extending from Isparta (Aksu) to Antalya (Serik) and fall into the Mediterranean Sea were investigated. The study area was investigated between February 2008-January 2009 at 7 stations selected from the spring point to the custarine zone. The measured data were given as maximum, minimum and average: Water temparature 13.94 +/- 0.594 degrees C (26.4-4.3); pH 8.09 +/- 0.04 (8.87-6.74); conductivity 501.08 +/- 75.802 not equal S/cm (4470-188), turbidity 26.95 +/- 9.55 NTU (605-1); bicarbonate (HCO-(3)) 197.99 +/- 8.92 mg/L (322.08-122); carbonate (CO-(3)) 5,74 +/- 0,926 mg/L (16.20-0.00); chloride (Cl-) 68.52 +/- 28.16 mg/L (1432.32-2.8); ammonium nitrogen (NH4-N) 0.09 +/- 0.016 mg/L (0.84-0.00); nitrite nitrogen (NO-(2)-N) 0.005 +/- 0.0008 mg/l (0.04-0.00); nitrate nitrogen (NO-(3)-N) 0.42 +/- 0.033 mg/L (1,26-0,00); phosphate phosphorus (PO-(3)(4)-P) 0.12 +/- 0.047 mg/L (3.71-0.00); dissolved oxygen 8.92 +/- 0.237 mg/L (13.40-5.6); organic matter 1.252 +/- 0.068 mg/L (3.68-0.28), biochemical oxygen demand (BOD5) 3.10 +/- 0.20 mWL (6-1), total hardness 22354 +/- 11.347 mg/L (750-114); sulphate (SO24-) 27.39 +/- 10.826 (570-0.25); calcium (Ca+2) 57.35 +/- 1.522 (103.8-34.6); magnesium (Mg+2) 19.93 +/- 2.47 mg/L (0.36-126.20); salinity 0.25 +/- 0.05 ppt (0.1-2.6). Consequently, it can be said that Koprucay River has first class quality according to the physico-chemical parameters, but becomes under pressure because of the pollution periodically.