Since Trousseau’s time numerous studies have addressed the relationship between cancer and venous thromboembolism (VTE) providing firm evidence of the increased risk of subsequent clinically overt malignancy during the follow-up of patients with idiopathic VTE. These malignancies are not limited to certain subtypes, but involve virtually all body systems. This knowledge has led to a long-standing debate on the need to screen for occult malignancies patients with idiopathic VTE with no clinical evidence of cancer at the time of the index thrombotic event. In fact the high incidence of newly discovered cancers does not automatically imply that screening is indicated in these patients since it is unknown whether a substantial proportion of cancers can be diagnosed, whether the diagnosed cancers are treatable and what the impact on cancer-related mortality is. Proper clinical trials are being conducted to find an answer to these questions.