This lecture note is useful to students of health science, medicine and other students and academicians. It is believed to provide basic knowledge to students on medical parasitology. It also serves as a good reference to parasitologists, graduate students, biomedical personnel, and health professionals. It aims at introducing general aspects of medically important parasites prevalent in the tropics and in Ethiopia in particular. It is our belief that this note will contribute much in alleviating the shortage of Parasitology texts.