PURPOSE OF REVIEW The discovery of a pleural effusion in the setting of lung cancer has diagnostic, prognostic, and therapeutic challenges, some of which are addressed in this review. RECENT FINDINGS Around 20% of patients with lung cancer have minimal pleural effusions, which are not amenable to a diagnostic thoracentesis. These patients have a poorer overall survival (∼7.5 months) than those without effusions (∼12-18 months), although slightly better than those with proven malignant fluids (∼5.5 months). Tumor genotype techniques are feasible on pleural fluid specimens and clinically helpful in identifying patients who may benefit from targeted therapies. If limited pleural involvement is detected during lung cancer surgery despite the presurgical imaging studies, macroscopic complete resection of the lung tumor is still a treatment option. Cytological examination for cancer cells in pleural cavity washings at the time of thoracotomy (pleural lavage cytology) is recommended to uncover pleural dissemination. Patients with non-small cell lung cancer with visceral pleural invasion might be considered candidates for postsurgical adjuvant therapy. SUMMARY Some predictors of adverse survival in patients with lung cancer include the presence of a minimal pleural effusion, positive pleural lavage cytology, visceral pleural invasion on pathologic examination, and unexpected pleural involvement during surgery.