Over the last 25 years the discipline of health economics has developed substantially. As an applied discipline, it has adapted and changed over time in response to the changing concerns of policy-makers, planners and managers. This paper questions whether it is like a chameleon, changing its appearance in response to the external environment, or like the leopard that never changes its spots. In answering the question, the paper presents an overview of the development of health economics as it has been applied in low and middle income countries distinguishing three eras, the 1970s, 1980s, and 1990s, and argues that in each of these eras the preoccupations of health economists have been somewhat different. In each era the key contributions of health economics are identified. The paper ends by considering future research priorities, and the obligations of developed country institutions in terms of research topics and mode of work.