Six months after right-sided spontaneous pneumothorax developed in a 56-year-old man, squamous cell carcinoma was discovered in the ipsilateral lung. Fifteen cases of bronchogenic carcinoma presenting as spontaneous pneumothorax have been reported in the English language literature. Possible pathogenetic mechanisms include: direct tumor invasion of pleura; rupture of a subpleural bleb (in an area of obstructive emphysema) or an emphysematous bulla (in an overexpanded portion of the lung associated with lobar or segmental collapse); or unknown. Patients with spontaneous pneumothorax who fail to achieve complete expansion after three weeks of therapy or who have persistent roentgenographic pulmonary infiltration should undergo further investigation for bronchogenic carcinoma.