Parasitic diseases still affect millions of people every year, especially in the tropics, causing considerable morbidity or death. Such infections within livestock are probably an even bigger problem, leading to poorer productivity, condemna tion of infected meat and considerable economic loss. Para sitological research has, however, helped the situation in some cases and the development of novel drugs, vaccines and diagnostics has improved our chances of controlling these diseases. Research into parasitic infections is, therefore, often goal orientated. However, the study of parasites and host/parasite relationships still remains one of the most exciting and in teresting aspects of biology. Scientists, from undergraduate students to research professors, frequently ponder over how endoparasitic organisms can survive within the most alien of environments - inside another organism. The nutritional, reproductive and survival strategies which have evolved within each group of parasites have allowed the development of highly specific host-parasite relationships and allow the successful transmission of the parasite from one host to an other. A considerable amount of research is therefore direc ted at improving our understanding of various aspects of parasite biology.