This experiment was undertaken to observe the effect of multi-level laminnectomy on the cervical spine of the growing cat. The changes in the structures such as ring apophysis, end-plate and epiphyseal plate were studied roentgenologically and histologically. Gross cervical kyphosis, the so-called "swan neck deformity", was developed in these segments where the laminectomy was performed. 1. Cervical kyphosis gradually developed in growing cats from postop. 4 months, while normal cervical curve could be maintained in adult cats. 2. Corporal subluxation at the kyphotic segment was detected from postop. 4 months, but wedge-shaped deformity of the vertebral body did not develop until postop. 12 months. 3. Histologically beak-like cartilagenous proliferation was observed at the anterior inferior margin of vertebral body at postop 6 months. Later it became ossified to form claw spur at postop 12 months. The cartilagenous end-plate was replaecd by fibrous connective tissue from postop. 6 months. 4. There was no evidence of thinning or early fusion of anterior part of the physis throughout the study period. It was found that the post-laminectomy kyphosis was developed as the result of forward subluxation of the vertebral bodies due to surgically induced posterior instability.