• Thirty-nine patients with clinical, histologic, and immunofluorescence evidence of leukocytoclastic (necrotizing) vasculitis were studied for the presence of circulating immune complexes. These patients were selected prospectively during a three-year interval from patients seen in a dermatology clinic. Clinical and serologic data are summarized and representative cases are presented. This large series of patients with leukocytoclastic vasculitis emphasizes both the frequency of this disorder and the varied disease settings within which it may manifest. The immunopathologic data presented support an immune complex-mediated pathogenesis for this disease process. (Arch Dermatol 1982;118:296-301)