The Dunedin Multidisciplinary Health and Development Study are an ongoing longitudinal investigation of health and behavior of a complete birth cohort that was drawn from the greater Dunedin metropolitan area, located in the southern coastal region of New Zealand's South Island. This chapter describes the methods used to develop and carry out the Dunedin Study, and how research using the Dunedin Study data is conducted. Location data are used by a "sample tracer" who is employed at each assessment to track, locate, and recruit Study members. The Dunedin Study uses a prospective-longitudinal, correlational design. The basic strategy of the Dunedin Study involves testing for causal relations within this correlational design. The Dunedin Study has comprehensive biomarkers of metabolic, liver, kidney, cardiovascular, dental, immune, and respiratory function, facial aging, and telomere length measured repeatedly at ages 26, 32, 38, and 45 years.