The present work deals with the ecology of eight species of freshwater ostracods (Cypridopsis vidiui, Potamocypris variegattf. Hemicypris dematomarginata, llyocypris gibha, Uyocypris hiplicata, Fabaeformisccmdona holzkampfu Pseudocandona semicognita and Limnocythere inopinata) collected from Qena Govemorate. Monthly samples were collected for a period of one year (from July, 2000 till June, 2001) from four sites. Some ecological factors were measured during the period of investigation and correlated with the density of the ostracod species studied. Statistical analysis was performed by using SPSS software package (version 9) and the model equations controlling the density and the physical factors measured for the studied species were deduced.