Children with idiopathic congenital bilateral vocal cord paralysis (BVCP) were investigated by electromyography (EMG) of the posterior cricoarytenoid and thyroarytenoid muscles to determine whether laryngeal EMG findings had diagnostic or prognostic significance. Four children between 3 weeks and 33 months of age were studied. Three had abductor paralysis and were tracheostomy-dependent, while the fourth had adductor paralysis requiring a feeding gastrostomy. Two of these patients also had other anomalies. Motor unit potentials showing phasic bursts with respiration were found in all four cases, while three children developed a full interference pattern on lightening of the anesthetic. Follow-up for between 37 and 52 months showed no significant clinical improvement in any of the patients. While the diagnosis of idiopathic congenital BVCP can represent a heterogeneous group of conditions, the findings suggest that normal laryngeal EMG findings may be a feature of idiopathic congenital BVCP but do not imply a favorable prognosis for early recovery. They may, however, have implications to explain the likely site of lesion in idiopathic congenital BVCP.