Method of sampling in a study of older people with a comparison of respondents and non-respondents.

Edinburgh is divided into 23 city wards in 10 of which one of us (J.W.) and colleagues provide a geriatric service. The sample was drawn from these 10 wards, contact being made with persons in the sample through their general practitioners. Ninetyfive general practitioners were working in 50 practices with premises in this area. The plan was explained to the doctors, 91 of whom agreed to co-operate and allowed us access to their lists of patients held by the Edinburgh Executive Council. A census was made from the records of the Executive Council of the name, address, date of birth, and National Health Service number of all those persons born in 1905 or earlier who lived in the defined area and who were on the list of a doctor with a surgery address in that area. There were 26,903 such persons. This population excludes those who were not on a doctor's list and those who lived in the area but attended a doctor with a surgery address outside the area. The National Health Service number helps to trace persons who have died