In order to protect the water quality of our water resources, aquatic ecosystem and public health, countries set limit values for hazardous and toxic chemicals in their laws and regulations related to water quality. In our country, the environmental quality standard values defined for inland waters and coastal transitional waters in the Surface Water Quality Regulation (10.08.2016, RG: 29797) entered with Regulation of Setting Environmental Targets for Surface Waterbodies (21.07.2020, RG:31192) by mid of 2020 . In this study, the results of 6-period water quality monitoring studies carried out in a total of 59 stations in 9 urban and 18 industrial discharges with 32 river stations on the main tributary of the Küçük Menderes River and its connecting tributaries. Water quality results were evaluated according to Annex-5, Table 4 and Table 5. According to the findings, 329 priority substances and specific pollutants were detected at all monitoring stations. Among these detected substances, 31 parameters in rivers, 16 in urban points and 31 parameters in industrial points exceeded the AA-EQS values. Obtained findings in this study are pioneering studies conducted in the basin. At the end of the evaluation, it is aimed to determine the substances exceeding the environmental quality standard value in the receiving water body and to establish a relationship between the substances exceeding these values and possible point sources. Thus, it will be possible to switch from technology based discharge limits to receiving water body discharge limits approach by determining the water quality in terms of priority substances and specific pollutants in Küçük Menderes River with the obtained findings.