There is a high incidence of thrombosis in cancer patients. Retrospective studies indicate that lupus anticoagulant (LA) antibodies can be a thrombosis risk factor in cancer. In 77 patients with different forms of cancer LA and thrombosis incidence were retrospectively evaluated. In a prospective study, with 42 lung adenocarcinoma patients, we measured plasma LA, fibrinogen, factor VIII (FVIII), and thrombosis incidence. A high frequency of LA and thrombosis were observed in both studies. In isolation LA, increased levels of FVIII and fibrinogen could not be considered good markers for the development of thrombosis.