The monorail Guidezilla guide extension catheter was designed to provide additional backup and facilitate device delivery in percutaneous coronary intervention (PCI) for complex coronary anatomy such as chronic total occlusion (CTO), extreme vessel tortuosity, diseased bypass grafts, and anomalous coronary arteries, among others.The present retrospective, single-center study included 188 consecutive patients who underwent PCI using the Guidezilla catheter from March 2015 to August 2016. Study outcomes were rates of target lesion crossing success, procedural success, and complications.The Guidezilla catheter was used most commonly in PCI of CTOs (45%) and heavy proximal calcification (37%), followed by tortuosity (10%), previously deployed proximal stents (4%), and coronary artery anomaly (4%). The right coronary artery (48%) was most commonly intervened followed by the left ascending (35%) and left circumflex (17%) arteries. Rates of target lesion crossing success and procedural success were both 99%, with one device-related periprocedural complication, namely proximal vessel dissection secondary to deep insertion which was successfully treated with stent implantation. Ninety percent of PCI were performed and completed successfully by radial access.In a single center with experienced operators, the use of the Guidezilla guide extension catheter in PCI of complex coronary anatomy performed mostly via radial artery access appeared safe and efficacious, and greatly facilitated device delivery.