A case of Kaposi's sarcoma in a child with no serologic evidence of human immunodeficiency virus (HIV) infection is reported. A 7-year-old boy with Stage IV non-Hodgkin's lymphoma, after conventional chemotherapy, underwent autologous bone marrow transplantation (ABMT). Five months later he presented with supraclavicular mass and mediastinal enlargement. A bone marrow biopsy showed hypoplasia with no signs of the underlying disease, whereas the excised mass revealed a typical histologic pattern of Kaposi's sarcoma. The child is currently being treated with recombinant alpha-interferon (alpha-IFN) and regression of the disease has been achieved.