This paper discusses the strategies used to construct scientific medicine in mid-Victorian Britain. An opening section considers why it was thought desirable to create a properly scientific medicine, and outlines the empirical and rational bases of the medical establishment's projects for this. The bulk of the paper concerns an alternative approach to making medicine scientific--that put forward by certain advocates of homoeopathy--and how this approach was excluded from those arenas where scientific medicine was being created, and thereby made unscientific. This process is illustrated by the clash between homoeopathy and establishment medicine that occurred in mid-Victorian Cambridge. The final section briefly considers the complementary process of educating the public in what was properly scientific medicine, and what was not, and suggests that the processes of building boundaries to exclude competing practitioners, while keeping patients inside, created the space in which modern scientific medicine has flourished so successfully.