The sudden infant death syndrome (SIDS) is among the leading causes of post-neonatal mortality in industrialised countries. Research has highlighted that many of these deaths are avoidable by adopting a few simple precautions. These include sleeping in the supine position, avoiding exposure to tobacco smoke, breast feeding where possible, and avoiding over heating. The paper traces the development of understanding of the role of sleeping position in the aetiology of SIDS and the diffusion of this knowledge among and within industrialised countries. In retrospect, evidence began to become available in the early 1980s but it was several years before it was acted upon, initially in The Netherlands and subsequently in New Zealand, the United Kingdom and Scandinavia. Several countries have mounted major national preventive campaigns, of various kinds, each of which has been associated with a reduction in deaths from SIDS, but others have not. The reasons for these differences are explored. The evidence for a causal link between sleeping position and SIDS is now very strong and the costs of implementing a policy to change behaviour is small, compared with other health care interventions. This information is now widely available in the international literature. The example of SIDS provides information on the barriers to adoption of knowledge as well as the factors that promote it.