In the past year, the major contributions to our understanding of Churg-Strauss syndrome and polyarteritis nodosa were the development of classification criteria by which to separate these from other vasculitides. The absence of granulomas in most biopsies from patients with Churg-Strauss syndrome was noted. Other reports suggested that allergic disease may be only one of the hypereosinophilic conditions that predispose to this form of vasculitis. Eosinophilia and vasculitis occurring in a patient after dietary supplementation with L-tryptophan were reported, and the prominent cardiac involvement in Churg-Strauss syndrome was reemphasized. Impressive responses of that disease to cyclophosphamide were documented in one patient. In the American College of Rheumatology Vasculitis Classification Study, polyarteritis nodosa was one of the hardest vasculitides to distinguish. Several reports reiterated the serious risk of major pulmonary hemorrhage from microscopic polyarteritis of the lung, which probably represents aforme frusteof Wegener's granulomatosis. Although no new studies of therapy in polyarteritis were reported, a review of infections in such patients indicated that exposure to more than 15 mg/d of prednisone correlated with infectious complications, and that intra-abdominal infections were particularly problematic.