This thesis is concerned with hospital-centred networks of non-commercial groups and their role in the dynamics of medical innovation. By breaking down `technology' into artefacts, techniques and regimes, we distinguish between two modes of technological change that underlie the evolution of healthcare services. These are `artefact-led technological change' and `technique-led technological change'. Artefact-led technological change is well characterised in the existing literature and follows from the development of novel services based on artefacts created by networks of firms and clinicians. By contrast we identify technique-led technological change as a comparatively under-explored area. We argue that the careers of technologies entering the clinic as a result of the development of novel techniques do not rely on firms in this way and may principally be developed within networks of non-commercial groups. We suggest these technologies follow a distinct dynamic that we characterise through a multiple-case empirical study. The empirical research centres on the genetic testing services of the UK's National Health Service (NHS). Using Blume's (1992) conceptual framework founded in the `sociology of technology', we explore the careers of our case studies longitudinally; analyse the changing interorganisational structures between actor groups; and examine the ways in which the problematisations of these groups shape the technology and its applications. Our findings indicate that industrial groups play little part in technique-led technological change until these technologies are relatively well established. After this point firms may create a role for themselves by facilitating specialisation and automation processes. We note that the early stages of technique-led technological change often occur in the absence of formal regulatory processes. Diffusion and change take place largely in an ad hoc, `bottom-up' manner, often reliant on bootlegged resources, charitable donation, or special initiatives. Although free from commercial constraints in the early phases, we find that the diffusion of technique-led technologies remains constrained within limits imposed by the tacit nature of skills, the availability of local resources and sets of professional norms.