Severe clinical ovarian hyperstimulation syndrome (OHSS) may occur after ovarian stimulation with gonadotropins A hypercoagulable state, a serious form of OHSS, is due to hemoconcentration as a result of a shifting of the intravascular fluid into the third space. Antiphospholipid syndrome is also a well-known hypercoagulable state, which manifests as an arterial or venous thrombosis and recurrent fetal loss. If OHSS, combined with a hypercoagulable state, such as antiphospholipid syndrome, develops, the potential of a thrombosis can be synergistically enhanced, creating a vicious cycle that results in serious thromboembolic complications. A 30-year-old woman, with an unusual right internal jugular venous thrombosis, occurring secondary to the development of OHSS and antiphospholipid syndrome, was treated.