The onset of peripheral ulcerative keratitis in the course of a connective tissue disorder, such as rheumatoid arthritis, relapsing polychondritis, or systemic lupus erythematosus, may reflect the presence of potentially lethal systemic vasculitis. Moreover, peripheral ulcerative keratitis may be the first sign of systemic necrotizing vasculitis in patients with Wegener's granulomatosis, polyarteritis nodosa, microscopic polyangiitis, or Churg-Strauss syndrome. Although the exact pathogenesis of this severe corneal inflammation and destruction is not well understood, evidence points to a dysfunction in immunoregulation with immune complexes formed in response to autoantigens or to some unknown microbial antigen depositing in scleral and limbal vessels. These events lead to changes that are mainly responsible for the resulting tissue damage. In pauci-immune vasculitides positive for antineutrophil cytoplasmic antibodies, cell-mediated cytotoxicity may play an important role in the pathogenesis of peripheral ulcerative keratitis. Untreated systemic conditions such as those mentioned above may carry a grave prognosis for the eye and may also be life-threatening. Immunosuppressive therapy with corticosteroids and cytotoxic agents is, we believe, mandatory in the treatment of these multisystem disorders associated with vasculitic peripheral ulcerative keratitis.