The transmissible spongiform encephalopathies (TSE), or prion diseases are a group of transmissible neurodegenerative disorders of humans and animals. Although the infectious agent (the 'prion') has not yet been formally defined at the molecular level, much evidence exists to suggest that the major or sole component is an abnormal isoform of the host encoded prion protein (PrP). Different strains or isolates of the infectious agent exist, which exhibit characteristic disease phenotypes when transmitted to susceptible animals. In the absence of a nucleic acid genome it has been hard to accommodate the existence of TSE strains within the protein-only model of prion replication. Recent work examining the conformation and glycosylation patterns of disease-associated PrP has shown that these post-translational modifications show strain-specific properties and contribute to the molecular basis of TSE strain variation. This article will review the role of glycosylation in the susceptibility of cellular PrP to conversion to the disease-associated conformation and the role of glycosylation as a marker of TSE strain type.