Congenital muscular torticollis (CMT) results from tightness of neck musculature that causes the infant to tilt the head to one side and turn it to the other side. Infants with CMT also show unequal use of both sides of the body for movement and play. In this randomized clinical trial, researchers will compare two physical therapy (PT) treatment methods, passive stretching and Perception-Action (P-A) Approach, in their effects on head position and use of both sides of the body in infants with CMT. Behavior demonstrated during PT sessions by infants in the two groups will be also compared. Thirty-six infants with CMT will be randomly assigned to a passive stretching group or a P-A Approach group. The infants in both groups will attend 5 weekly PT sessions, including the initial evaluation, 3 subsequent weekly sessions, and a re-evaluation session. At visits 1 and 5, each infant's habitual head position, the ability to turn the head to both sides, muscle strength on both sides of the neck, motor development, and use of both sides of the body for movement and play will be assessed. Each infant's behavior exhibited during therapy will be assessed at visits 2-4. Results obtained from the two groups will be compared.