Zooplankton refers to the weakly swimming animals inhabiting aquatic habitat. It plays an important role in the aquatic ecosystem since it is considered as a primary consumer transferring energy to higher ones in the food web. Crustacean zooplankton constitutes a major part of zooplankton which includes Copepoda, Cladocera and Ostracoda. The present book is the outcome of several taxonomic works started in 1987 and concentrated on the freshwater crustacean zooplankton of Egypt. It includes 145 figures and keys illustrating the morphology of these groups. Also previous works on the ecology of the groups are summarized. No doubt, the book will help workers all over the world to identify these important groups and to understand their ecology and distribution. This will initiate subsequent studies on the groups.