Abstract Information from the Human Genome Project will be vital for defining the genetic
and environmental factors that contribute to health and disease. Well-designed case–control
studies of people with and without a particular disease are essential for this, but rigorous
and unbiased conclusions about the causes of diseases and their population-wide impact
will require a representative population to be monitored over time (a prospective cohort
study). The time is right for the United States to consider such a project.