A series of 30 children with the right middle lobe syndrome had cough and asthmatic-like wheezing. Pneumonia or bronchitis characterized by recurrent localization in the middle lobe of the right lung were constant findings. Respiratory symptoms were refractory to usual treatment. Abnormal findings on chest x-rays and bronchograms showed complete or partial atelectasis of right middle lobe in all cases. In some children, decreased vital capacity with normal one-second forced expiratory volume and laboratory signs of infection were present. The condition appeared twice as frequently in girls as in boys, and symptoms usually began at 1 to 2 years of age, although diagnosis was rarely made before 6 years of age. Twenty-three of the 30 children were atopic, and 18 of the 30 had family histories of allergy. Treatment consisted of lobectomy in ten (all of whom improved considerably). On conservative medical management alone, this condition was controlled in ten, eight were unimproved, one was lost to follow-up, and one died.