The BHPS was an annual survey consisting of a nationally representative sample of about 5,500 households recruited in 1991, containing a total of approximately 10,000 interviewed individuals. The sample was a stratified clustered design drawn from the Postcode Address File and all residents present at those addresses at the first wave of the survey were designated as panel members. These same individuals were re-interviewed each successive year and, if they split-off from original households to form new households, they were followed and all adult members of these households were also interviewed. Similarly, new members joining sample households become eligible for interview and children were interviewed as they reached the age of 16. Since 1994, children aged 11-15 also completed a short interview.
Extension samples of 1,500 households in each of Scotland and Wales were added to the main BHPS sample in 1999 to enable independent analysis of each country. In 2001 a sample of 2,000 households was added in Northern Ireland. The total sample size for the BHPS including the extension samples was around 10,000 households across the UK. The extension samples allow for country specific and comparative research within the UK.