Sporadic Creutzfeldt-Jakob disease (sCJD) is the most common form of human transmissible spongiform encephalopathies (prion disease), but its cause has not been fully elucidated. According to its biochemical properties prion protein is resistant to routine sterilisation methods. Thus, invasive medical procedures could be involved in the genesis of the disease. Present knowledge about iatrogenic routes of transmission, oral infection and transmission via blood products in variant CJD (vCJD) underlines the importance of careful surveillance and analysis of potential routes of transmission. Several studies of risk factors for sCJD published in the past have given contrary results, which may be largely explained by different control groups. This article reviews epidemiology and classification of CJD and discusses possible risk factors and summarizes previous case-control studies.