In the last fifteen years, substantial progress has been made in identifying why some people are particularly susceptible to specific infectious diseases. Extensive evidence has accumulated that host genes are important determinants of the outcome of infection for many common pathogens. This book summarises advances that have been made in understanding the complexity of host genetic susceptibility. The diseases covered include those of great public health importance such as malaria and HIV, and those of topical interest such as Creutzfeldt-Jakob disease. Many different techniques have been used to identify host genes involved in infectious disease susceptibility. Each chapter describes how these discoveries were made and the book is therefore useful to anyone planning genetic studies on a multi-factorial disease, regardless of whether it has an infectious etiology.