Why does the World Health Organization (WHO) put emphasis on neglected tropical diseases (NTDs)? What are the NTDs? Are NTDs found in the United States? Is there any relationship between coronavirus disease 2019 (COVID-19) and NTDs? These are some of the questions being addressed in the book.The aim of this textbook is to introduce a modern synthesis on human parasites of medical importance. Species of parasitic protozoa and helminths are presented in detail, from history and discovery to aspects of genomes and molecular biology, together with life cycle, therapy, drug resistance, and case studies of parasitic diseases useful to the clinicians.