We describe six electrosurgical incidents and one complication which occurred during guidewire-assisted sphincterotomy. Studies were conducted on three types of guidewires: Teflon painted, Teflon sheathed, and polymer coated. Scanning electron micrographs demonstrated surface imperfections in the painted Teflon guidewire coating, which allowed for potential electrical short circuits between cutting wire and guidewire through a septal defect in a double channel catheter. Septal defects were found in 25% (1 of the 4 tested) of the factory fresh sphincterotomes that were used in this study, and in 10% (6 of 57) of those used clinically. Induced current (capacitively coupled) present on the guidewires was measured at 13 to 30 mA for typical sphincterotomy settings. The induced current on sheathed guidewires, without any insulation defects, was measured at less than 1 mA at typical operating powers. As both short circuits and induced currents place the patient at risk for burns or perforation at the distal end of the guidewire, we suggest the use of a Teflon-sheathed rather than Teflon-painted guidewire, if the wire is to be left in place during sphincterotomy. The Teflon sheath offers the thickest insulation, a very low probability of surface defects, and therefore a high index of safety.