Large-scale population cohorts such as the UK Biobank are transforming the way we consider and pursue genetic analyses, offering the opportunity to learn about a whole range of human traits and diseases. Here I will describe genome-wide association analyses of over 4,000 distinct traits and diseases from the UK Biobank including estimation of heritability. Further, we performed sex-stratified analyses enabling us to probe the question of the degree to which genetic influences on complex traits are shared across men and women. Previous work on sex-stratified analyses has shown that height and BMI are largely similar but that waist-hip ratio shows clear evidence of sex-specific effects (Randall et al. PLoS Genetics, 2013). Analysis of the initial wave of UK Biobank shows differences in sex-specific estimates of heritability for waist circumference, blood pressure, skin and hair color (Ge et al, PLoS Genetics, 2017). Initial results suggest that the overwhelming majority of genetic influences are shared across the sexes, with an average genetic correlation estimated to be in excess of 90%. Nevertheless, a number of phenotypes do show sex-specific genetic correlation clearly less than 1 including fat percentage traits, exercise related traits such as pulse rate and haemoglobin concentration and prior history of smoking. These kinds of analyses illustrate the growing potential for biobanks to understand the impact of genetic variation across all of human health and disease.