Kaposi's sarcoma (KS) is a pleomorphic spindle cell lesion whose incidence has markedly increased among patients infected with the human immunodeficiency virus (HIV), especially among those whose primary risk factor is homo/bisexual transmission. The question as to whether KS is even a true neoplasm still remains largely unsettled due to the body of epidemiologic and histologic evidence suggesting an infectious etiology of the lesion. Accordingly, very few studies have been published regarding systemic distribution or patterns of metastatic progression of the lesion. In the past, such studies have been primarily hampered by inadequate sampling of different tissue specimens and by the lack of a method whereby the data could be rationally interpreted. In the present study we have reviewed the clinical and pathologic features of 169 autopsied patients with either documented HIV infection or the acquired immunodeficiency syndrome, among whom 28 patients were found to have KS. Using cluster analysis, we constructed a novel data structure, called a "dendrogram," whereby patterns of metastasis could be examined. Our results show at least three patterns of metastasis of the lesions, predominantly involving the skin, upper gastrointestinal tract, or midgastrointestinal tract, within this cohort of autopsied patients. These three patterns suggest that there is no single pathogenetic mechanism in the acquisition and dissemination of HIV-associated KS.