The dynamic flexometer: an instrument for the objective evaluation of spasticity. Anesthesiologists may care for patients who have spasticity in the operating room or pain clinic. A number of therapeutic modalities for treatment of spasticity exist, but there are few simple objective methods for evaluating their effect. We describe one instrument, the Dynamic Flexometer, that measures the force required to move the limb passively through its maximum range of motion. The data presented validate the instrument's reliability. Two clinical cases presented here demonstrate the instrument's utility. This device may be of value to anesthesiologists involved in the care of patients with spasticity. 