Title. The Internet as a research site: establishment of a web-based longitudinal study of the nursing and midwifery workforce in three countries. Aim. The aim of this paper is to describe the development of a web-based longitudinal research project, The Nurses and Midwives e-cohort Study. Background. The Internet has only recently been used for health research. However, web-based methodologies are increasingly discussed as significant and inevitable developments in research as Internet access and use rapidly increases worldwide. Method. In 2006, a longitudinal web-based study of nurses and midwives workforce participation patterns, health and wellbeing, and lifestyle choices was established. Participating countries are Australia, New Zealand and the United Kingdom. Data collection is handled through a dedicated website using a range of standardized tools combined into one comprehensive questionnaire. Internet-specific data collection and a range of recruitment and retention strategies have been developed for this study. Discussion. Internet-based technology can support the maintenance of cohorts across multiple countries and jurisdictions to explore factors influencing workforce participation. However, barriers to widespread adoption of web-based approaches include website development costs, the need for fast broadband connection for large data collection instruments, and varying degrees of Internet and computer literacy in the nursing and midwifery workforce. Conclusion. Many of the issues reported in this paper are transitional in nature at a time of rapid technological development. The development of on-line methods and tools is a major and exciting development in the world of research. Research via the world-wide web can support international collaborations across borders and cultures.