The present study reviews the experience with six infants and young children who had malfunction of the diaphragm and were treated at the UCLA Hospital during the past ten years. Three had true eventration with aplasia or atrophy of the muscle fibers. Two sustained phrenic nerve injury at birth, resulting in phrenic paralysis. One infant had the unusual malformation of phrenic nerve agenesis, associated with phocomelia and agenesis of the left lower lobe of the lung. Phrenic plication produced immediate relief of respiratory distress in five of the infants, each of whom is alive from six months to eight years postoperatively. The condition of one with phrenic nerve and Erb's palsy improved without operation.