We report the cases of two males who presented with spontaneous complete unilateral pneumothorax with ipisilateral liquid effusion. Neither had a history of previous respiratory disease. In both cases chest tube drainage resulted in recurrence of pneumothorax with chronic illness requiring surgical exploration. The surgery revealed a malignant pleural mesothelioma by histological examination. Thus, spontaneous pneumothorax, particularly with abondant effusion can be a revealing symptom of malignant pleural mesothelioma.