The "buddy" wire technique, i.e. the use of a second 0.014 inch guide wire placed alongside the one employed to advance balloons and stents inside the coronary artery during percutaneous coronary intervention (PCI), may help in a series of procedural challenges during PCI. Indeed, by improving both the stability of the guiding catheter and the support for balloon and stent, a buddy wire use is sometimes the simplest way to accomplish a successful procedure. In this paper, we discuss technical aspects of some specific circumstances frequently encountered during PCI, in which a buddy wire may be helpful. These include: 1) The reduction of balloon slippage during angioplasty for in-stent restenosis; 2) insufficient back-up of the guiding catheter; 3) stenting of lesions located in vessels with proximal tortuosities/angulations; 4) stenting of lesions distally located in the vessel; 5) facilitation in the positioning of distal protection devices; 6) stenting of a lesion distally located from a previously implanted stent or from a coronary segment with both calcification and sharp bend; 7) PCI on coronary arteries with anomalous origin. Because of its simplicity, low cost, and availability, the use of a buddy wire should be considered when dealing with the aforementioned conditions during PCI procedures. © 2005 HMP Communications.