BACKGROUND: Therapeutic plasma exchange (TPE) is the first-line therapy for patients with thrombotic thrombocytopenic purpura (TTP). However, therapeutic response to TPE and late prognosis vary among different patients, and predictors of these outcomes may help customize treatments to individual patients. STUDY DESIGN AND METHODS: We retrospectively examined the platelet (PLT) recovery rate (PRR) in 64 consecutive patients with initial episode of TTP who received TPE in our institution between 2003 and 2010. PRRs were calculated by linear regression of the PLT counts at the start and during the first few days of TPE treatment. Its relationship with remission in response to TPE, exacerbation and relapse, and survival was analyzed by univariate and multivariate analysis. RESULTS: With multivariate analysis, which included ADAMTS13 activities, patients with a PRR by Day 3 (PRR3) of 5 × 109/L per 24 hours or above were 18 times more likely to achieve remission in response to TPE than those with a lower PRR3 (p < 0.001). In addition, short-term exacerbations and relapses beyond 1 month of remission occurred almost exclusively in patients with a PRR3 of 5 × 109/L per 24 hours or above. Survival was significantly better in these patients than in patients with PRR3 below the cutoff (p < 0.001), and the hazard ratio adjusted for ADAMTS13 and age was 23.2 (p < 0.005). CONCLUSION: PRR3 with a cutoff of 5 × 10 9/L per 24 hours provides a practical approach to risk stratify TTP patients receiving TPE early in their treatment and may guide the decision making both at initial encounters and during the long-term follow-up.