The traditional treatment of pneumothorax has been with a chest tube and hospitalization. A series of 35 patients with 41 pneumothoraces treated on an outpatient basis is presented here. A no. 12 chest tube connected to a Heimlich valve led to successful treatment in 88 percent of the cases. Failure of treatment requiring hospitalization occurred in 12 percent of cases and was due only to persistent air leaks. No complications occurred.