It has been estimated that approximately one fifth of the world"s population is carrying one or more of the parasitic organisms which cause malaria schistosomiasis, trypanosomiasis and other debilitating diseases. The study of these immensely successful organisms has traditionally drawn on many disciplines, especially microbiology, immunology and biochemistry. Over the last decade, parasitologists have acquired an additional and very powerful tool in the form of molecular biology and its associated technology. This has led to the analysis of parasitic systems in detail undreamed of only a generation ago. As the picture of molecular actions and interactions builds up, so new aproaches to combatting parasites suggest themselves. This introduction to molecular parasitology will be of interest to parasitologists and molecular biologists alike and explores this subject at a level which will be accessible to undergraduate students while being sufficiently up-to-date and referenced to be of value to post-graduates and more senior workers moving into or currently active in this area.