The Helsinki studies comprise two cohorts: first, 7,086 people born at Helsinki University Hospital during 1924-33; second, 13,345 people born at the University or Midwives’ Hospital during 1934-44. Maternity records/Hospital Birth Records are linked to childhood measurements of height and weight from six-monthly school checks. The second cohort also includes height and weight measurements from infant welfare clinics – the average number of measurements is seventeen. Early records provide socio-economic data based on occupation and housing. In later adulthood, the surviving cohort members have been followed-up at clinic visits and through questionnaires. This work is conducted with our colleagues in Helsinki.