Deep venous thrombosis of the upper extremity (DVTUE) is a rare thrombotic disorder that may occur spontaneously but is most often related to predisposing factors, such as an indwelling central venous catheter, malignancy, or exercise. The role of coagulation disorders, i.e., a hypercoagulable state in the pathogenesis of DVTUE is not well known. We have evaluated both genetic and acquired thrombophilia parameters in consecutive patients with DVTUE. A hypercoagulable state was found in 32% of the patients. The most frequent coagulation abnormality was the presence of lupus anticoagulant or anticardiolipin antibodies (27%). Factor V Leiden mutation was detected in two patients, antithrombin deficiency in one, and none of the patients had the prothrombin G20210A gene variant or protein C or S deficiency. The prevalence of coagulation abnormalities was not significantly different in a subgroup of patients with spontaneous DVTUE as compared to those with an obvious predisposing factor, such as an indwelling central venous catheter. We conclude that antiphospholipid antibodies are frequently found in patients with DVTUE. Factor V Leiden mutation, prothrombin 20210A gene variant, protein C deficiency, and protein S deficiency do not seem to play a major pathogenetic role in DVTUE.