Significant eosinophilia is a prominent feature in Churg-Strauss syndrome but has only rarely been described in Wegener's granulomatosis (WG). We describe two Wegener's granulomatosis patients with > 30% eosinophilia on their initial presentations. Other etiologies that could account for their eosinophilia were excluded. Both patients had pulmonary alveolar hemorrhage, sinusitis, arthritis, high-titer cytoplasmic antineutrophil cytoplasmic antibodies (cANCA), and proteinase-3 antibodies, but no evidence of renal disease. Herein we discuss eosinophilia, the differential diagnosis of pulmonary infiltrates and eosinophilia, the role of cANCA in vasculitis and autoimmune disease, compare Wegener's granulomatosis and Churg-Strauss syndrome, and review possible pathogenic mechanisms.