Abstract: A writing instrument includes an advance-retract mechanism for projecting the writing tip from within the barrel for employment of the writing instrument, and retracting the tip to a point within the barrel, when the writing instrument is not in use. A plunger assembly includes a rotatable knob which is disposed at the top of the barrel and is interconnected to a finger which contacts the cam surface of a slidable actuator. Rotation of the knob in one direction advances the writing tip from within the barrel and opposite rotation of the knob is effective to retract the writing tip into the barrel.