Air-fluid levels appearing in lung bullae are always considered to indicate infection and therefore conservative management with prolonged antibiotics and observation to resolution is the recommended approach. This article presents a case of bullous lung disease with new air-fluid levels, in which a diagnosis of malignancy was made by aspiration of the fluid. This association is discussed and a more aggressive evaluation of such patients to include computed tomography of the chest and fluid sampling is recommended before a presumption of benignity is made.