A young woman with recurring bouts of thrombotic thrombocytopenic purpura presented an opportunity to study a single patient serially and in depth. This patient underwent 12 remissions in response to fresh frozen plasma, and as little as 250 ml of plasma or plasma from which cryoprecipitate had been extracted with efficacious. Neither the Lian factor nor alterations in either cold-insoluble globulin or protein C could be demonstrated. Evidence in support of the concept of "exhausted" platelets was generated, in that immediately before a thrombocytopenic relapse, platelet function was altered as manifested by bruising, prolongation of the bleeding time, and decreased platelet aggregation. The in vitro addition of normal plasma to such platelets did not improve aggregation. The antiplatelet agent sulfinpyrazone did not seem to add efficacy. Serial observations support the hypothesis that the progression of pathophysiologic events in this patient is: exhausted platelets, thrombocytopenia, hemolysis, renal perturbations, and central nervous system dysfunction.