In 1994, Statistics Canada began data collection for the National Population Health Survey (NPHS), a household survey designed to measure the health status of Canadians and to expand knowledge of health determinants. The survey is longitudinal, with data being collected on selected panel members every second year. This article focuses on the NPHS sample design and its rationale. Topics include sample allocation, representativeness, and selection; modifications in Quebec and the territories; and integration of the NPHS with the National Longitudinal Survey of Children. The final section considers some methodological issues to be addressed in future waves of the survey.