Ulnar nerve lesions may occur at different sublocations at wrist and may involve various branches of the nerve. Standard neurophysiological studies are generally insufficient in revealing these lesions. Demonstration of conduction block and/or focal slowing of nerve conduction is the most definitive electrodiagnostic evidence for the localization of segmental demyelination. Short-segment incremental study (SSIS) is a sensitive technique for detecting the ulnar neuropathy at the wrist (UNW). We report 3 cases of UNW caused by ganglion cysts in Guyon's canal which were studied by using SSIS across the wrist. Even though SSIS is a time-consuming and technically demanding method, it increases the electrodiagnostic potential of detecting segmental demyelination in this location.