In a prospective investigation of isolated simple pneumothorax, the treatment of 35 patients with a total of 37 pneumothoraces was studied. A standardized sequential treatment approach was followed for evacuation of the pneumothorax and maintenance of lung reexpansion. The protocol involved catheter placement using a Seldinger technique, aspirations, and documentation of reexpansion by chest radiography and observation. Reaccumulation of air was treated with Heimlich valve attachment to the catheter at intrapleural pressure and further observation. Continued air leak following Heimlich valve attachment was treated with chest catheter suction using a Pleurovac at -20 cm H2O pressure. Chest tube thoracostomy was performed for continued failure of reexpansion. In 22 of the 37 pneumothoraces (59%) simple catheter aspiration maintained lung reexpansion without complications. In the remaining 15 pneumothoraces (41%), seven (47%) responded to Heimlich valve attachment, and three (20%) maintained expansion with chest catheter suction. Chest tube thoracotomy was required to maintain expansion in 33% (five) of those who failed catheter suction (14% of all pneumothoraces studied). Patients treated successfully with simple catheter aspiration were sent home. Patients requiring a Heimlich valve, chest catheter suction, or chest tube thoracostomy were hospitalized. Use of these catheter techniques resulted in lower cost and was associated with shorter hospitalizations than in chest tube thoracostomy. Our study suggests that sequential treatment of simple pneumothorax should be considered as a cost-effective and therapeutically successful alternative to immediate chest thoracostomy in selected cases.