To clarify the clinical status of blood purification therapy (BPT) in critical care in Japan, we conducted a cohort study using data from a nationwide registry of the Japan Society for Blood Purification in Critical Care in 2013. We enrolled 2227 patients treated with BPT (female, 39.1%; mean age, 65.5±12.1years) in the intensive care units of 43 facilities. Patient characteristics, modes of BPT, and survival rate for each disease were investigated. In total, BPT was performed 3053 times. Continuous renal replacement therapy (CRRT) (57.9%) was the most common mode of BPT, followed by intermittent renal replacement therapy (20.2%) and direct hemoperfusion with the polymyxin B-immobilized fiber column (PMX-DHP) (11.5%). Nafamostat mesilate (84.9%) was most frequently used as the anticoagulant. The 28-day survival rate was 56.8% in all patients. The most common mode for acute kidney injury (AKI) and multiple organ failure was CRRT, while PMX-DHP and CRRT were most common for sepsis. There was no significant difference in survival rates among AKI stages 1-3. Survival rate (38.3%) was significantly lower in patients with acute lung injury (ALI) than in those with multiple organ failure (41.8%) and those with sepsis (46.6%). Multivariate regression analysis revealed that the APACHE II score and the presence of acute ALI and acute hepatic failure were significantly associated with death. This large-scale cohort study showed the clinical status of BPT in Japan. Further investigations are required to clarify the efficacy of BPT for critically ill patients.