Venous thromboembolism (VTE) is a well-recognized complication of autoimmune haemolytic anaemia (AIHA), and is a major cause of morbidity and mortality in this disorder. However, the incidence, pathogenesis and risk-factors for VTE in AIHA remain poorly defined. Lupus anticoagulants (LA) and anticardiolipin (ACA) antibodies are autoantibodies directed against epitopes on prothrombin or beta2 glycoprotein I (beta2-GPI). Both LA and ACA (together called antiphospholipid antibodies, APLA) are associated with VTE. We have prospectively studied the occurrence of VTE and APLA in 30 patients with AIHA. VTE was objectively documented in eight (27%) patients. APLA were detected in 19 (63%) patients with AIHA, of whom nine (30%) had a LA and 17 (57%) ACA. Seven patients had both LA and ACA. Among the eight patients with VTE, LA was detected in five (63%) and ACA in four (50%). There was a statistically significant association between presence of LA and occurrence of VTE (RR: 7.50, 95% CI: 1.25-45.2, P = 0.03). VTE is a frequent and life-threatening complication of AIHA. Detection of the lupus anticoagulant in patients with AIHA identifies individuals at significantly increased risk for VTE. Future studies should address the role of prophylactic anticoagulation in patients with AIHA.