Two young children, 5 and 30 months of age, developed acute transient dyskinesias. The novel features of these patients were classic orobuccal-lingual dyskinesias, their young ages, and the association with asthma and theophylline. The movements resembled tardive dyskinesias of older patients on neuroleptics, but neither patient had any exposure to neuroleptic drugs. Choreiform movements were moderately severe and remitted several hours after discontinuation of theophylline or over days in the patient who remained on the drug. No symptomatic treatment of dyskinesia was required. Both infants otherwise had normal neurologic examinations with no clinical evidence of meningoencephalitis, seizures, or stroke. Both infants required hospitalization for respiratory distress, but not intensive care. The highest theophylline levels measured in these patients were 22 and 25 micrograms/ml and levels determined closest to the appearance of dyskinesias were lower. Urine toxicology screen for other drugs and routine blood work were normal. The infants, examined subsequently for 1 1/2-2 years for asthma, have demonstrated no reappearance of dyskinesias or other neurologic abnormalities. We propose an interaction of theophylline, hypoxemia, or other factors related to asthma in the pathophysiology of reversible dyskinesia in our patients.