A second questionnaire survey of Japanese patients with thrombotic microangiopathy (TMA) was carried out to investigate the frequency, laboratory abnormalities and outcome in 2004 and 2005. The first and second surveys evaluated 397 patients including 19 with familial TMA and 378 with acquired TMA. The patients with acquired TMA included 165 with Escherichia coli O-157 infection-related TMA (O-157 TMA), 70 with ADAMTS13-related TMA (ADAMTS13 TMA) and 38 with other types of TMA (other TMA). The rate of ADAMTS13 TMA was significantly higher in patients with collagen diseases than in patients with all other underlying diseases (p < 0.001). The treatment of acquired TMA included plasma exchange (PE), steroids, antiplatelet agents, and anticoagulants, PE was carried out in 91.4% of patients with ADAMTS13 TMA, 68.4% of patients with other TMA and 12.7% of patients with O-157 TMA. The efficacy of PE and steroid therapy tended to be higher in patients with ADAMTS13 TMA than in those with other TMA. The complete remission rate was the highest and the mortality rate was the lowest in the patients with O-157 TMA. The mortality rate tended to be lower in patients with ADAMTS13 TMA than in those with other TMA. However, not all of the patients in our study were examined for ADAMTS13 at the time that this questionnaire survey was conducted.