R esearch into the pathogenesis, prevention, and control of infectious and parasitic diseases remains a global priority, as these scourges continue to be a substantial cause of mortality and morbidity. The plethora of molecular tools that are now readily available has facilitated a genome-wide approach to studying the pathogenesis of such diseases, with direct implications for disease prevention and treatment. The articles in this Review Series describe how genome-wide approaches have provided insight into a range of human pathogens, leading to greater understanding of the human diseases that they cause, and highlight some of the challenges that must be overcome if we are to maximize what we learn from the wealth of genomic information now available.