A ''disease'' is any impairment of normal physiological function affecting all or part of an organism, especially a specific pathological change caused by infection, stress etc., producing characteristic symptoms. As such disease is a condition of the body or a part of it in which functions are disturbed or deranged. A disease may be caused by excess or deficiency or absence a disease agent which can be a substance or a force. The disease causing biological agents are called parasites and their study is called parasitology. Parasites have a direct impact on humans or on domesticated animals that is almost beyond comprehension. The world has become smalle1,and parasites can travel faster. In some instances our own changing social patterns have also created a more favourable environment for parasites. A variety of factors thus make parasitology a subject of increasing concern for the medical profession. No doubt, medical students and physicians as well as other paramedical professionals such as medical technologists, nurses and public health personnel should have a basic grounding in the diagnosis, prevention and treatment of human parasitic infection. The aim of the present work has been, and continues to be, to provide such fundamental information.