The author claims that the positional cloning approach, whereby a gene is identified by its map position without making assumptions about its structure or function, has provided significant information about common inherited disorders. Genes responsible for cystic fibrosis, Duchenne muscular dystrophy, and neurofibromatosis have been cloned. However, this technology has been labor intensive and extremely expensive. The Human Genome Project will provide information that will drive research for at least the next 100 years and will likely transform medicine in the 21st century into the preventive mode.