This paper was prepared for the International Review of Psychiatry as part of an effort to improve understanding of the connection between employee health and performance and to begin to identify new strategies through which treating wellness as an investment in human capital can lead to greater organizational success. Computer database searches of peer-reviewed literature published between 1993 and 2005 and manual reviews of 20 journals were used to identify research on the link between employee health and performance. Data was extracted to summarize the overall findings on the magnitude of health problems addressed by health promotion and disease prevention programmes, and the impact of interventions on improving health risk, reducing health care cost, and improving worker performance. From this summary, major conclusions on early detection of disease, the impact of behaviour change programmes were drawn. This systematic review is supplemented with a case study description of a preliminary evaluation of a corporate wellness programme in a major international organization. The influence of developments in work/family issues, complementary and alternative medicine, and quality of care and health outcomes research are briefly discussed. Finally, a conceptual framework for studying the impact of health and productivity is described.