There is an emerging trend worldwide toward outcome measurement as a means of demonstrating the value of health services provided. There are a number of issues associated with this. A variety of events and circumstances may influence outcomes, such as pre existing conditions, timing of health service delivery, general health status on admission together with processes of service delivery, interventions initiated, the quality of services provided by a variety of health professionals and support staff. In addition there are definitional issues, data structures, coding and classification issues, computing, information and communication technological issues, privacy issues, the need for standards and benchmarks. This paper identifies health outcomes research efforts, and initiatives undertaken to resolve some of these issues. The paper argues that unless nursing data are included in national statistical data collections nursing’s contribution to healthcare will remain largely invisible. It concludes by examining nursing’s contribution towards the development of an international unified nursing language and classification system needed to achieve this aim.