In order to determine the benthic faunal composition of the Tahtal? Reservoir, which has al-most 23 km² surface area and is located in 40 km south of Izmir, samples were taken from three stations between May 2006 and April 2007 in monthly intervals. As a result of the study, 14 taxa were determined. Of the determined taxa, 4 species (Limnodrilus hoffmeisteri, Limno-drilus udekemianus, Aulodrilus pigueti, Dero digitata) belong to Annelida, 9 species (Chi-ronomus plumosus, Chironomus (Camptochironomus) tentans, Cryptocladopelma laccophila, Microchironomus tener, Polypedilum nubeculosum, Polypedilum (Tripodura) scalaenum, Cri-cotopus (Isocladius) intersectus, Psectrocladius (Psectrocladius) limbatellus, Procladius (Holotanypus) sp.) to Chironomidae and a species (Pontogammarus robustoides) belongs to Amphipoda. When the results were carried out quantitatively, 82% of the macrobenthic invertebrate fauna of the reservoir was represented by Chironomidae larvae. Similarly, 17% and 1% of the fauna were represented by Oligochaeta and Amphipoda specimens, respectively. Meanly, 452 ind/ m² were found on the bottom of the reservoir. Among the investigated stations, the richest one was the third station (53.33%) followed by the second (34.55%) and the first one (10.12%), respectively. The second station was the richest one (12 taxa) and followed by the third (10 taxa) and first (6 taxa) ones, qualitatively.