In patients infected with human immunodeficiency virus (HIV), thrombotic thrombocytopenic purpura (TTP) appears to follow a heterogenous clinical pattern. There are few studies looking prospectively at their outcome. We compared the clinical characteristics and response to therapy in consecutive patients with TTP and tried to define the differences between the HIV positive and negative groups. Patients with TTP were evaluated clinically and with standard tests. Patients were then treated with infusions of cryoprecipitate poor fresh frozen plasma (FFP)(30 mL/kg/day) until normalization of the platelet count. Patients were given daily furosemide according to clinical needs. In responding patients FFP was tapered off by 200 mL every 3rd day. In addition, all received prednisone 1mg/kg until FFP therapy was discontinued. Patients who developed fluid overload, and who failed to respond within 48 Hs or deteriorated at any time were referred for apheresis of 1½ plasma volume until response. Similar tapering off with plasma infusions would then proceed in responsive individuals. Of 45 patients with TTP 21 were HIV+. This disorder was dominant among black females (20/21). HIV+ patients had significantly lower presentation Hb (5.8 [range 3.9–9.8] g/dL; p= 0.03), platelet count (13 [range 7–49] x 109/L; p= 0.05) and a CD4 count of 0.096 x 109/L, indicating advanced disease. However, except for one, all HIV+ subjects responded rapidly to FFP infusions. The platelet count and LDH levels normalised significantly faster than HIV (−) group and in no case was apheresis required. 1 patient died of fulminant septicemia before response was documented. 10 HIV (−) patients with idiopathic TTP required apheresis due to oliguria (n= 4) or disease progression (N= 6; 25%). Of these, 4 died of TTP despite apheresis. The remainder (n= 6) as well as those not requiring apheresis, improved. Response in the 2 groups was at a median of 41(HIV+) and 96 (HIV−) units (U= 220 mL. plasma) of FFP (p= 0.004) respectively. Three patients relapsed and two responded to a further course of FFP and splenectomy. 5 individuals with AIDS died of opportunistic infections. Overall 84% responded to this protocol, which was particularly favourable in patients with HIV infection (95% response). Multiple regression analysis showed that the favorable factors for response were HIV+ status (p= 0.002), younger age (p= 0.0001) and no need for apheresis (p= 0.00). Factors associated with improved survival were younger age (p= 0.001), rapid platelet (p= 0.001) and Hb (p= 0.0009) recovery, and lower number of FFP units to normalize LDH (p= 0.006). We conclude that while compared to classic (HIV(−)) TTP, patients who are HIV+ seem to be more commonly seen among African Black patients with advanced infection. In these patients, response to plasma infusion therapy seems significantly better and faster. This observation is important particularly when apheresis is not available as happens in remote rural areas in developing countries. In these patients, once the diagnosis is established, adequate volume of FFP should be infused without delay.