This article considers naturalistic analyses of the concepts of health and disease in light of the possibility of constructing novel living systems. The article begins by introducing the vision of synthetic biology as the application of engineering principles to the construction of biological systems, the main analyses of the concepts of health and disease, and the standard theories of function in artefacts and organisms. The article then suggests that reflection on the possibility of artefactual organisms amounts to a challenge to the functional theories of health and disease proposed by Wakefield and Boorse. More specifically, Wakefield and Boorse's theories are reconstructed as responses to a dilemma concerning how to allow for the ascription of health and disease to artefactual organisms without at the same time opening up the possibility of diseased nonliving artefacts such as cars and computers. It is argued that neither response will enable us to ascribe health and disease to artefactual organisms, because both theories, in order to rule out the possibility of ascribing health and disease to nonliving artefacts, make such ascriptions conditional on having a natural-selection history or being part of a species which has been designed by evolution.