An ultrasonic surgical instrument includes an elongate substantially rigid probe and an elongate tubular sheath member. The probe is operatively connected at a proximal end to a source of ultrasonic mechanical vibrations and has a distal tip configured for transmitting ultrasonic vibration energy into organic tissues. The probe longitudinally traverses the sheath member. The sheath member has a distal edge with a first portion on one side of the probe and a second portion on an opposite side of the probe. The first portion of the distal edge of the sheath member is disposed substantially closer than the second portion of the sheaths distal edge to the distal tip of the probe. The second portion of the distal edge is so spaced from the distal tip as to permit effective visualization of the distal tip during use of the instrument.