On the Sakarya River which is one of the importants rivers of Turkey, has been determined innumerous living kinds of algae in the samples taken from the part where polluted water such as Ankara brook and Porsuk brook mixed with the Sakarya River. it has also been found out that there are indicator algae types that are tolerant to pollution in the Sakarya River by forming relationship between these algae and physical and chemical qualities of the water.