Medical protozoology is the science which deals with study of medical protozoa, this study focus on definition, biology and life cycles, mode of transmission of diseases, epidemiology, pathology, diagnosis, treatment and prevention and control of protozoan infections. Protozoa are unicellular single celled organisms which included four types according to movement: pseudopoda, ciliates, sporozoa and flagellates which are divided into three types according to habitat: blood and tissues flagellates, intestinal flagellates and uro-genital flagellates. The trophozoite and cyst stage are two diagnostic life-cycle stages which are commonly seen in protozoa. Protozoa caused dangerous effects on human body like: toxic effect; these produce allergy or necrosis, anaemia, loss of weight, fever and abortion or congenital anomalies. The objective of this book is to help medical and medical laboratory students to understand the protozoan infections and how to diagnose them.