The NHSCR (National Health Service Central Register) was used to trace 6,803 men and women born in North Hertfordshire between 1920 and 1930, for whom birth and infancy data had been recorded. The NHSCR identified 2,621 men and women as resident in the UK in 1994; 1,428 of these were still resident in North Hertfordshire. With permission from their GP, we invited these men and women to participate in a home interview and clinic at which a wide panel of markers of ageing were characterised (including grip strength, cognitive function, anthropometry, visual acuity and lens opacity, hearing threshold and skin thickness). This first HAS follow-up was conducted between 1994 and 1995 when the participants ranged in age from 63 to 73 years. A second follow-up was conducted in 2003-05, a median of 9 years after the first follow-up, when participants were aged 72-83 years.