Catheter allotopia is a common complication associated with totally implantable access ports (TIAPs) that can lead to premature catheter removal or other secondary risks. Timely detection and treatment are critical to achieving a satisfactory outcome. Totally implantable access ports are safe, efficient, lowrisk, and easy-to-maintain medical devices that provide reliable venous access in patients receiving long-term intravenous infusion. They were first used in cancer therapy in 1982. 1 There are some not insignificant immediate and longterm complications associated with TIAPs including catheter allotopia, pneumothorax, arrhythmia, catheter embolism and infection, and pinch-off syndrome. Catheter allotopia is a common reason for premature catheter removal. Here, we report 3 clinical cases of catheter allotopia in which the TIAP catheter migrated to the azygos vein (AV, Case 1), internal thoracic vein (ITV, Case 2), and lower craniocerebral segment of the right internal jugular vein (IJV, Case 3). We also discuss this issue in the context of the literature. 2 | CASE REPORTS 2.1 | Case 1 A 58-year-old woman was diagnosed with ovarian cancer with peritoneal metastasis. We planned to use the docetaxel plus cisplatin regimen for chemotherapy after she underwent ovarian cancer reduction surgery. Since ultrasonic examination revealed that the patient's right IJV was too thin for catheter insertion, left vascular access was selected and the port was subcutaneously implanted in the left infraclavicular