My research interests lie in developing an understanding of the control complex traits, where inter-individual variation within and between populations is controlled by variation at a number of genes (often referred to as quantitative trait loci or QTL), by environmental factors and by the complex interactions of these components. Most variation between individuals within and between populations is in the form of complex traits. Consequently variation in complex traits is responsible for most inter-individual variation in susceptibility to disease (both infectious and metabolic) in humans, livestock and other species and underlies responses to selection, both artificial selection in livestock and natural selection in all species. We can only be really effective in understanding and treating many diseases, in predicting individual’s risk of developing particular conditions and in dissecting the causes and consequences of natural selection if we understand the genetic control of variation in complex traits.