Clinically significant respiratory failure in a group of animals with an experimentally produced structural thoracic scoliosis was identified. A detailed physiologic investigation of their respiratory function showed that their respiratory compromise was associated with the development of a smaller and stiffer chest. Frank respiratory failure, however, was rare and seen only in animals with the most severe spinal deformities when it was also associated with a general failure to thrive. Animals with less severe deformities had little measurable restriction of pulmonary function, did not develop respiratory failure, and grew normally.