See also Lowe GDO. Epidemiology of venous thromboembolism: the need for large (including prospective) studies and meta-analyses. This issue, pp 2186–8 and El-Galaly TC, Kristensen SR, Overvad K, Steffensen R, Tjønneland A, Severinsen MT. Interaction between blood type, smoking and factor V Leiden mutation and risk of venous thromboembolism: a Danish case–cohort study. This issue, pp 2191–3.