In order to determine the Chironomidea (Diptera) fauna of Gediz Delta, seasonal samplings were carried out between February 1998 and May 1999 at 16 stations. Physico-chemical measurements from the 16 stations of the River Gediz showed that temperature values are between 8ºC and 31ºC, dissolved oxygen values are between 0 mg/l and 14 mg/l ; pH values are between 7 and 9.93 and salinity values are between 0.56‰ and 38.8‰. An Ekman–Birge Grab (15x15 cm) was used in benthic samplings. Sampled materials were sieved through a 0.5 mm mesh sized sieve and fixed in 70% alcohol. As a consequence of the study, totaly 22 taxa were determined. Of the determined taxa, 4 species belong to Tanypodinae subfamily of the Chironomidae family, one belongs to Orthocladiinae and 17 belong to Chironomidae.