A previously unrecognized, striking movement disorder has been observed in 10 premature infants with severe bronchopulmonary dysplasia. Chronic hypoxemia, hypercarbia, bronchospasm, and inadequate nutrition were present in all. The movement disorder developed from approximately the third postnatal month. The dominant movements involve the limbs, neck, trunk, and oral-buccal-lingual structures. The limb movements were most prominent distally and consisted of rapid, random, jerky movements (similar to chorea) and "restless" movements (similar to akathisia). Similar movements of the neck and face were observed; tongue movements had a "darting" quality. The oral-buccal-lingual movements were similar to the dyskinesia of older patients. Movements were exacerbated during episodes of respiratory failure and attenuated during sleep. All infants exhibited feeding disorders, largely due to tongue movements. In 3 infants treated with clonazepam, there was striking improvement in motor function, including feeding. The natural history was partial or complete resolution or a static course. Thus, of the 7 surviving infants, the movements were absent (without therapy) at 15, 18, and 30 months of age. In the remaining 4 infants (3 of whom receive clonazepam), the movements, though attenuated, persisted at 6, 12, 15 and 21 months of age, respectively. Neuropathologically, 1 infant showed neuronal loss with astrocytosis in caudate, putamen, globus pallidus, and thalamus. These data defined a previously unrecognized extrapyramidal movement disorder of infants with severe bronchopulmonary dysplasia; pathogenesis may be related to chronic hypoxemia.