The healthcare professions have never been static in terms of their own disciplinary boundaries, nor in their role or status in society. Healthcare provision has been defined by changing societal expectations and beliefs, new ways of perceiving health and illness, the introduction of a range of technologies and, more recently, the formal recognition of particular groups through the introduction of education and regulation. It has also been shaped by both inter-professional and profession-state relationships forged over time. A number of factors have converged that place new pressures on workforce boundaries, including an unmet demand for some healthcare services; neo-liberal management philosophies and a greater emphasis on consumer preferences than professional-led services. To date, however, there has been little analysis of the evolution of the workforce as a whole. The discussion of workforce change that has taken place has largely been from the perspective of individual disciplines. Yet the dynamic boundaries of each discipline mean that there is an interrelationship between the components of the workforce that cannot be ignored. The purpose of this paper is to describe four directions in which the existing workforce can change: diversification; specialisation and vertical and horizontal substitution, and to discuss the implications of these changes for the workforce.