Thrombotic thrombocytopenic purpura (TTP) is a rare and life-threatening thrombotic microangiopathy characterized by thrombocytopenia, microangiopathic hemolytic anemia, and microvascular thrombosis causing neurological and renal abnormalities; it is associated with massive depletion of platelets in the microvasculature to form microthrombi1 . Long-term follow-up of patients with congenital TTP (cTTP) revealed frequent strokes and renal injury. Of 217 surviving patients, 62 (29%) had a stroke; the median age was 21 years. iTTP patients also require long-term follow-up. iTTP patients with low ADAMTS13 activity (\<70%) in remission have a 28% risk of stroke. Survival rates of iTTP patients in remission were lower than those of age-, race-, and sex-matched populations. In terms of stable treatment, maintenance therapy is not recommended for patients with iTTP. Previous studies have shown that aspirin may be able to prevent stroke complications in patients with cTTP and iTTP. In addition to its potential efficacy, the risks of aspirin are small and inexpensive. Aspirin is very effective in secondary prevention of stroke 6. However, the therapeutic value of aspirin in TTP has not been studied previously. To improve the prognosis and survival of patients with cTTP and iTTP, we propose to conduct a prospective study to observe the efficacy and safety of aspirin in patients with cTTP and iTTP in remission.