We reviewed the case histories and roentgenograms of 50 patients with spontaneous pneumothorax who underwent small lumen catheter aspiration. The results were analyzed with regard to the presence or absence of preexisting lung disease. Patients with no history of previous lung disease and no roentgenogram abnormality other than the pneumothorax had a 66 percent chance of successful reinflation using the technique of manual aspiration described here. Patients with evidence of tension pneumothorax, bullae, pleural adhesions, and active tuberculosis were treated unsuccessfully. None of the patients experienced any complication from this procedure. Our results indicate that many patients with spontaneous pneumothorax may be quickly and successfully treated with small lumen catheter manual aspiration.