The clinical manifestations, pathologic findings, and responses to therapy were reviewed in eight patients with thrombotic thrombocytopenia purpura (TTP). Only one exhibited all five cardinal manifestations; five showed a triad of anemia, thrombocytopenia, and neurologic abnormalities. Microangiopathic red cell changes on peripheral blood smear and severe thrombocytopenia were present in all. The serum LDH levels were initially elevated in all eight; this enzyme determination was extremely useful for following the course of the disease and its response to therapy. Pathologic evidence of TTP was most consistently found in lymph nodes, spleen, and bone marrow biopsies. All patients were treated with a combination of therapeutic modalities including plasma exchange with replacement by fresh frozen plasma. Using this approach, 7/8 entered a complete remission; however, disappearance of all clinical manifestations was not seen in two patients prior to splenectomy.