There are currently 3-5 million cases of leishmaniasis in the world and the prevalence is rising. The first chapter in this volume reviews the cell biology of the parasite and its transmission and survival. The second review addresses the apicomplexan protozoan parasites _Theileria anulaga_, _T. parva_ and _T. sergenti_ which globally cost agriculture over one billion US dollars annually. Current research in this area aims to produce effective, stable and cheap subunit viruses requiring only a single application and the authors predict that success will eventually be achieved with 'naked DNA' vaccines containing cytokine genes as immunopotentiators. The next review is the first in over 30 years to discuss the larva of the class Monogenea.The authors cover morphology, behaviour and structure of many examples providing a detailed reference for researchers. The penultimate chapter discusses the distribution of _Schistosoma bovis_ and considers the reported interactions occurring between parasites and snails. The final chapter reviews one of the most serious parasitic diseases in salmonid aquaculture - sealice. In 1998 the costs due to sealice damage in Scotland alone were estimated at 15-30 million pounds. Discussion of biology and control of these ectoparasites emphasizes the need to understand the basic biology of the parasite. This volume will be essential reading for parasitologists in many branches of the subject.