A method for detecting transverse mode vibrations in an ultrasonic hand piece/blade is achieved by monitoring the power delivered to the hand piece/blade to determine whether it increases as expected when power levels applied to the hand piece/blade are changed. While the blade is being held in midair, the power delivered to the hand piece/blade and/or the impedance of the hand piece/blade is measured at a first power level. Using the value obtained at the first power level, the expected power at a second power level is calculated and used to set a pass/fail threshold level for an actual measured power. Alternatively, the threshold is set for the impedance is set. Next, the actual power delivered to the hand piece/blade and/or the impedance of the hand piece/blade is measured at a level 5 power setting. A determination is made whether the hand piece/blade exhibits transverse mode behavior based on whether the actual measured power exceeds the established pass/fail threshold level. If this is the case, operation of the generator is inhibited, a "Transverse Mode Vibrations Present in Hand Piece/Blade" error code is stored in the generator, and a "Bad Hand Piece" message is displayed on a liquid crystal display on the generator. In addition, a method for detecting transverse mode vibration in an ultrasonic hand piece/blade is achieved by monitoring power delivered to the hand piece/blade to determine if the an extraordinary power increase occurs as the drive frequency is shifted downward and/or upward from a primary intended resonance operating frequency.