This study was conducted to determine physico -chemical characteristics and nutrient levels on a monthly basis of therivers of the Eastern Black Sea reg ion with an average flow rate of about 10 m 3/sec and above, including Kızılırmak,Yeşilırmak, Melet, Pazarsuyu, Aksu, Harşit, Değirmendere, Solaklı, İyidere, Büyükdere, Fırtına, Çağlayan and Kapistre.The highest annual average values for electrical conductivity (EC), reactive phosphate (o -PO4), ammonium (NH 4),nitrite (NO 2), sulphate (SO4) and hardness were determined as 1.16 ±0.29 mS/cm, 0.81±0.66 µM, 11.6±10.4 µM, 2.83±3.1µM, 333±74 mg/L ve 407±47 mg CaCO 3, respectively, in Kızılırmak (Samsun); the highest turbidity, total suspended solids(TSS) and organic matter (as permanganate index) as 191±99 FTU, 232±137 mg/L and 4.12±2.14 mg O/L respectively inDeğirmendere (Trabzon); the highest silicate concentration in Melet (Ordu) as 305±47 µM; the highest nitrate concentrationin İyidere (Rize) as 124 ±79 µM; and the highest chlorophyll-a levels in Yeşilırmak (Samsun) as 1.98±1.70 µg/L. As a resultof cluster analyses, it was established that Kızılırmak river is in a group different from that of other rivers in terms of s ulfate,hardness and electrical conductivity and the rivers situated in eastern part of the region is more acidic than those in the west interms of pH. Data obtained from the study were evaluated according to Water Quality criteria and water quality classes of therivers were identified by parameters.