Recent studies have better defined the epidemiology of venous thromboembolism (VTE) in cancer patients. The incidence is highest in patients who have metastatic disease at the time of presentation and who have fast growing, biologically aggressive cancers associated with a poor prognosis. The incidence is also high in patients with haematological cancers. Other specific risk factors that affect the incidence of VTE include undergoing invasive neurosurgery, the number of underlying chronic co-morbid conditions, and being of Asian/Pacific Islander decent (lower incidence). The incidence is highest in the first few months after diagnosis, which may reflect the biology of the cancer or medical interventions such as major surgery or start of chemotherapy. The development of VTE is clearly associated with decreased survival, and this effect is greater among patients initially diagnosed with local- or regional-stage cancer compared with patients with metastatic cancer, probably because VTE reflects the presence of a biologically aggressive cancer. Finally, a small percentage of patients with idiopathic VTE and no clinical or laboratory evidence of cancer may harbour an aggressive but 'occult' malignancy likely causally linked to the development of VTE.