Tracheomalacia is a rare congenital malformation of the tracheobronchial cartilages in which the supporting cartilaginous rings permit expiratory collapse of the airway. The condition is usually mild and self-limited. There is a severe variant, however, that is life-threatening and warrants separate categorization. Four children with severe primary tracheomalacia were treated recently. The clinical symptoms, diagnostic findings, and eventual treatment of these patients were highly distinctive and almost identical in all 4, permitting us to make the following observations: (1) primary severe tracheomalacia must be suspected in infants with unexplained respiratory distress manifested by stridor and cyanosis; (2) symptoms are not present at birth but appear insidiously after the first weeks of life, are markedly aggravated by respiratory tract infections, and are made worse by agitation; (3) bronchoscopy is essential for definitive diagnosis and should be employed early in the diagnostic process; (4) tracheostomy is probably essential in most instances; and (5) resolution, although spontaneous, does not occur until after 2 years of age.