OBJECTIVE Intravascular catheter procedures are often performed in patients undergoing antithrombotic therapy. However, methods for the management of antithrombotic agents in the perioperative period are currently unclear. Therefore, the safety and management of antithrombotic agents in these patients were investigated. METHODS A prospective, multicenter, observational study [Management of Antithrombotic Agents During Surgery or Medical Procedures with Bleeding (MARK study)] at 58 National Hospital Organization institutions in Japan was performed. 1,040 patients were enrolled in the MARK study and underwent an intravascular catheter procedure. For all participants, the details of the procedure, method of perioperative management of antithrombotic agents, and occurrence of thrombosis, embolism, and bleeding complications during the study period were investigated. RESULTS The use of antithrombotic agents was continued in 1,017 patients (98%, continuation group) and discontinued in the other 23 (2%, discontinuation group). Continuation of the antithrombotic agents did not have a significant effect on the overall occurrence of thromboembolism [hazard ratio (HR), 0.15; p=0.08] or bleeding events (HR, 0.19; p=0.12). However, the overall adverse event risk was significantly lower in the continuation group than in the discontinuation group (HR, 0.18; p=0.03). CONCLUSION It is both safe and appropriate to perform intravascular catheter procedures in patients continuing with antithrombotic therapy.