In order to determine the oligochaeta fauna of Lake Sapanca (Turkey) samples were collected from 5 stations monthly, between September 2000-August 2001. As a result of the study, 13 species, which belong to 9 genera, were determined. These species are Aulodrilus limnobius, Tubifex tubifex, Tubifex ignotus, Tubifex nerthus, Limnodrilus hoffmeisteri, Potamothrix hammoniensis, Potatnothrix vejdovskyi, Nais communis, Spirosperma ferox, Psammoryctides barbatus, Ilyodrilus templetoni, Psammoryctides deserticola, Paranais frici. Also some physicochemical parameters of the water (temperature, dissolved oxygen, pH, turbidity and depth) were measured at the sampling site. The average density of total oligochaetes in the benthos of the lake was 1,887 ind m(-2). According to Shannon-Wiener index, Lake Sapanca was found had 2.59 richness and, 5th station were found to have highest diversity (3.87) while 3rd station to have the lowest (1.59). There are almost no data on the Oligochaeta fauna of this lake so far. Hence, all the determined taxa from the localities are recorded for the first time.