BACKGROUND: Ethanol lock therapy (ELT) has been performed for the purpose of preserving central venous catheters (CVC) in central venous catheter-related blood stream infection (CRBSI), but evidence for its effectiveness is not established. We conducted a multicenter, prospective study on the ELT protocol to ascertain its safety and effectiveness against CRBSI. METHODS: The subjects were patients aged over 1 year with potential for developing CRBSI who had long-term indwelling silicone CVCs. After culturing the catheterized blood, a 70% ethanol lock was performed daily for 2-4 h for 7 days. The effectiveness rate of ELT for single and multiple courses, the presence or absence of relapse of CRBSI within 4 weeks of treatment, and whether the CVC could be salvaged after 4 weeks were examined. RESULTS: From September 2014 to August 2018, 49 cases from six hospitals were enrolled in the study. Catheter blockage was seen in one case and the CVC was removed. A single course of ELT was effective in episodes 88% (42/48). In the remaining three episodes that failed after a single course of ELT, a second ELT was performed; however, all were ineffective. In episodes 93% (40/42), no CRBSI relapse was seen up to 4 weeks after the end of treatment. In episodes 84% (41/49), the catheter could be preserved for 4 weeks or more after the end of treatment. Facial flushing was seen in two cases as an adverse event; however, this was transient and soon disappeared. CONCLUSION: ELT is effective for 88% of CRBSI and 84% of catheters can be salvaged; therefore, this protocol is considered useful. TRIAL REGISTRATION: UMIN000013677.