Systemic illnesses, such as vasculitides and systemic lupus erythematosus, may have ocular symptoms, or they may present with ocular signs and undiagnosed or occult systemic signs. The recently described ophthalmic and neurologic presentations and new diagnostic modalities for Wegener's granulomatosis, giant cell arteritis, and systemic lupus erythematosus are reviewed. Hypercoagulable states and their role in visual diseases are assessed, and strategies for evaluating patients with hypercoagulable states are described.