Malignant angioendotheliomatosis is a rare intravascular (angiotropic) lymphoma. Patients most often present with cutaneous or central nervous system findings. We describe three patients with malignant angioendotheliomatosis involving the skin. The initial lesions in each were tender, indurated nodules on the lower extremities, resembling inflammatory panniculitis. Skin biopsies and immunohistochemical studies from all patients confirmed intravascular B-cell lymphoma. Two patients had visceral involvement, and molecular genetics studies showed clonal immunoglobulin gene rearrangement in one. Electron microscopy in this case showed increased fibrin and atypical lymphocytes within blood vessels. Malignant angioendotheliomatosis is a monoclonal intravascular lymphoma, usually of B-cell phenotype. Occlusion of small blood vessels with lymphoid cells, fibrin, and degenerating cellular debris causes the cutaneous lesions. An excisional biopsy through the depth of subcutaneous tissue may be necessary to confirm the diagnosis of malignant angioendotheliomatosis.