The range of genetic diversity within human populations is enormous. Genetic susceptibility to common chronic disease is a significant part of this genetic diversity, which also includes a variety of rare, clear–cut, inherited diseases. Modern DNA–based genomic analysis can now routinely lead to the identification of genes involved in disease susceptibility, provides the basis for genetic counselling in affected families, and can be used more widely for a genetically targeted approach to disease prevention. This naturally raises problems concerning the use of information not just in an individulal's decisions, but also for employment, and health and life insurance.