Motor control evolves from a complex set of neural, physical, and behavioral processes that govern posture and movement. Motor skills are learned through interaction and exploration of the environment. Tone is defined as resistance of muscle to passive elongation or stretch when an individual attempts to maintain muscle relaxation. Tone may be due to physical inertia, intrinsic mechanical elastic stiffness of muscles and connective tissues, and reflex muscle contraction. Hypertonia, clonus, hypotonia, dystonia, rigidity, and synergy are the tonal abnormalities discussed in this chapter. A detailed discussion on abnormal synergy in upper and lower limbs and grading methods for manual muscle testing has been also presented in this chapter.