Population parameters ofDaphnia roseawere studied at various concentrations ofChlorellasp. (0.25, 0.75 and 3.0 mg C 1−1) at several temperatures (20, 25, 28, and 30 °C) in the laboratory. Although there were some differences in the degrees of the effects of the various temperature-food combinations, both food and temperature exerted influences on almost all of the main population parameters ofD. rosea. At a water temperature of 28 °C, growth and reproduction were reduced, and at the lowest food level (0.25 mgC 1−1), reproduction failed.D. roseadid not survive at 30 °C in spite of abundant food supply, indicating that 30 °C is a physiological limit.