HIV infection is known to be associated with endothelial dysfunction leading to thrombosis. We report a patient with multiple abdominal venous thrombosis and splenic hematoma who was seropositive for HIV-1. No cause for the hypercoagulable state was detected; prothrombin time, activated partial thromboplastin time, and levels of protein S, protein C and antithrombin III were normal. He tested negative for VDRL and anticardiolipin antibodies.