After eight years of planning, criticism, and debate, UK Biobank has begun recruiting its intended 500 000 volunteers. The first batch of 10 000 invitation letters began arriving last week at the homes of people aged 40-69 living in the Manchester area.

Recruitment is scheduled to last four years. The state of health of members of the resulting cohort will be tracked through medical records for at least the next three decades. Blood samples taken at the initial assessment will make it possible to compare these data with each person's genetic make- up. The ultimate aim of this large epidemiological …