Rotifera composition and vertical distribution in Aslantas Dam Lake was studied from April 2001 to March 2002. It was established that the rotifera were represented by 33 species and 2 subspecies in the lake. Total average density of the rotifera was found to be 255883 Rotifer/m3. Species such as Keratella cochlearis cochlearis, K. cochlearis tecta, Polyarthra dolichoptera, Trichocerca capucina and Asplanchna priodonta were present througout the year. The analysis for the determination of vertical distribution of Rotifera showed that the most abundant species at surface and below surface was P. dolichoptera with 34.59%, and K. cochlearis cochlearis with 29.29%, respectively. Rotifera had the highest density at 5 m in the lake. In addition, 63.58% of total Rotifera was observed in photic zone while the rest (36.42%) was collected from aphotic zone. Chlorophyll a measurement of the dam lake showed that the average montly values were 31.44 mg/m3 at the surface and 20.13 mg/m3 below the surface. A vertical increase at the value of chlorophyll a was observed from the surface to 7.5 m. Gradual decrease at the value was recorded exceeding the depth of 7.5 m.