OBJECTIVE A retrospective evaluation of the effectiveness of simple aspiration therapy in primary spontaneous pneumothorax was carried out. METHODS We enrolled 143 patients with mild and moderate primary spontaneous pneumothorax between June 2006 and October 2010. Clinical backgrounds and therapeutic results from 92 patients that underwent simple aspiration therapy were assessed. RESULTS All patients were treated safely without any serious complications. With the exception of one patient with an unknown result, the initial success rate after three days was 72.5% (66 out of 91 patients). Chest X-ray analysis at the first medical examination showed that the success rate was significantly low in patients with a larger vertical rim between the apex and top of the lung and a higher collapsed area ratio; in particular, the success rate was markedly decreased in cases that exceeded 8 cm and 50%, respectively. No significant difference was observed in the aspiration volume, however, the success rate was lower when the aspiration volume was more than 1,500 mL. The recurrence rate at one year was 36.4% (24 out of 66 successfully treated patients). CONCLUSION Our results are nearly identical to previous reports from other countries and show that simple aspiration has proved to be a safe and effective therapy.