This PhD thesis models individuals? health over the life course. The focus is on people with long term illnesses, on inequalities in health by socioeconomic status and on the impact of health on employment. The main tool of analysis is a dynamic microsimulation model of the Australian population which tracks the demographic, socioeconomic and financial characteristics of individuals and their families over the life course. In recognition of their in depth ability to analyse distributional and financial issues, the use of microsimulation models for policy analysis is rapidly increasing. The thesis describes the innovative health and socioeconomic modules added, and presents topical ? though illustrative ? applications of the enhanced model. One simulates the impact of narrowing inequalities as health is lifted nationally to the level currently enjoyed by the most affluent 20% of Australians. The other quantifies the likely impacts of longer working lives, which may arise from changes such as: more favourable labour market conditions; incentives to remain in the labour force longer; and general improvements in health.