The aim of this paper is to evaluate etiological accounts of functions for the domain of technical artefacts. Etiological theories ascribe functions to items on the basis of the causal histories of those items; they apply relatively straightforwardly to the biological domain, in which neo-Darwinian evolutionary theory provides a well-developed and generally accepted background for describing the causal histories of biological items. Yet there is no well-developed and generally accepted theory for describing the causal history of artefacts, so the application of etiological theories to the technical domain is hardly straightforward. In this paper we consider the transposition of etiological theories in general from the biological to the technical domain. We argue that a number of etiological theories that appear defensible for biology become untenable for technology. We illustrate our argument by showing that the standard etiological accounts of Neander and Millikan, and some recent attempts to improve on them, provide examples of such untenable theories.