Objective.-A clinicopathologic review of splenic involvement in Wegener's granulomatosis. Design.-A retrospective case review, spanning a 10-year period, identified five patients with Wegener's granulomatosis and splenic involvement. Setting.-A large teaching hospital and outpatient clinics. Interventions.-Cytotoxic therapy (cyclophosphamide and corticosteroids), mechanical ventilation in respiratory failure, renal hemodialysis in renal failure, and general supportive care. Results.-Necrotizing granulomatous inflammation and vasculitis with fibrinoid necrosis were found in the spleen in one antemortem case. At autopsy, two cases demonstrated extensive infarction; microscopic examination revealed parenchymal coagulative necrosis, microcalcification, and vascular thrombosis, but no evidence of vasculitis. Two other cases showed nonspecific changes of diffuse hyalinization of blood vessels, vascular congestion, and hemosiderin deposition. Conclusions.-Splenic involvement in Wegener's granulomatosis is rarely diagnosed during life, occurs more frequently than once thought, and can occasionally lead to considerable morbidity.