Transthoracic diaphragmatic plication is a simple and effective means of treatment for phrenic nerve injury and resultant diaphragmatic paralysis, and should be undertaken as soon as the diagnosis of diaphragmatic paralysis is established in a child with substantial respiratory difficulty. Seven of more than 1,500 patients sustained phrenic nerve injury during operation for congenital heart disease at our institution over the past five years. All but 1 patient were less than 5 months old, and the average weight was 3.8 kg. Five of the 7 could not be weaned from the ventilator, and the other 2 had persistent postoperative tachypnea and stridor. Before 1980, 3 patients were intubated for an average of 16 days prior to diagnosis by fluoroscopy. Since then, 4 patients have been intubated for an average of 7.8 days before diagnosis. All 7 underwent transthoracic diaphragmatic plication and were extubated by 6 days after operation (mean, 3.7 days). Six patients survived and are doing well. The 1 death occurred in 1976 in a premature infant with multiple congenital cardiac lesions; diagnosis was delayed until the twenty-eighth day after intubation and transthoracic diaphragmatic plication, until the sixty-second day. This infant died of pneumonia one month after extubation. These data support our policy of establishing an early diagnosis of phrenic nerve injury and early treatment utilizing transthoracic diaphragmatic plication in symptomatic children.