The Gediz River is one of the most important and main water source for the Gediz Basin of the Aegean region and Turkey. In this study, 18 water samples were collected from the source to the end of the river. Change in water quality, some trace elements and heavy metal contents of the Gediz River were determined. Analysis of the Fe, Cu, Mn, Zn, Pb, Cr, Co, Cd and Ni showed that the quantity of Fe in the eighth sample, taken before the meeting point of the Alasehir tributary-Gediz River and the quantity of Cr in the eighth sample were above the critical level. Overall, the study indicated that the quality of the water of the Gediz River deteriorated (along the river) from the source to the end. It was also determined that the N/P ratio diminished from the source to the end which is an indicator of domestic pollution. To preserve the soils and plants of the Gediz Basin, the Gediz River and its tributaries should be protected from garbage and effluents.